EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: usagi on August 03, 2015, 05:44:15 am
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Thread to collect all the bg7tbl information into a single reference.
A chinese ham "bg7tbl (http://bg7tbl.taobao.com/)" designed and manufactured a series of cheap GPSDO which are being sold on alibaba and ebay, typically for around $150USD.
There are a number of different versions, which can be identified by the date printed on the front panel:
"2014-11-06" (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg722792/#msg722792)
custom board with surplus russian morion mv89 (http://www.morion-us.com/catalog_pdf/MV89.pdf) OCXO. gps is u-blox. both sine and square wave output variants available.
"2014-12-09" (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg722794/#msg722794)
custom board with surplus russian morion mv89 (http://www.morion-us.com/catalog_pdf/MV89.pdf) OCXO. gps is u-blox NEO-6M-0-001 (https://www.u-blox.com/en/product/neo-6-series).
"2015-07-08" (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg722795/#msg722795)
custom board with surplus oscilloquartz star 4 (oscilloquartz "STAR 4" (http://www.oscilloquartz.com/product-star-4-696-108)) gpsdo board. OCXO is oscilloquartz 8663-XS. gps is u-blox LEA-5T-0-002 (https://web.archive.org/web/20150416233555/http://u-blox.com/en/lea-5t.html).
"2015-07-17" (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg722798/#msg722798)
custom board with surplus trimble "57963-D" gpsdo board. OCXO is trimble 73090. gps is unknown.
"2015-09-17" (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg813525/#msg813525)
custom board with surplus russian morion mv201 (http://www.morion-us.com/catalog_pdf/MV201.pdf) OCXO. gps is u-blox NEO-6M-0-001 (https://www.u-blox.com/en/product/neo-6-series)
"2015-09-17" (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg825017/#msg825017) (variant 1 - mv89a)
custom board with surplus russian morion mv89a (http://http://www.morion.com.ru/catalog_pdf/MV89-OCXO.pdf) OCXO. gps is u-blox NEO-6M-0-001 (https://www.u-blox.com/en/product/neo-6-series)
"2015-09-17" (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg990093/#msg990093) (variant 2 - bliley nvg47a1282 )
custom board with surplus bliley nvg47a1282 (http://web.archive.org/web/20160725005042/http://www.mikrocontroller.net/attachment/107430/6891__NVG47A1282_RoHS.pdf) OCXO. gps is u-blox NEO-6M-0-001 (https://www.u-blox.com/en/product/neo-6-series)
"2016-05-31" (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg1037770/#msg1037770)
custom board with surplus bliley nvg47a1282 (http://web.archive.org/web/20160725005042/http://www.mikrocontroller.net/attachment/107430/6891__NVG47A1282_RoHS.pdf) OCXO. gps is u-blox NEO-7M-0-000 (https://www.u-blox.com/en/product/neo-7-series)
AVR dump available in this post (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg1268759/#msg1268759).
"2017-03-29" (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg1261119/#msg1261119)
custom board with surplus cts 970-2178 OCXO. gps is u-blox NEO-7M-0-000 (https://www.u-blox.com/en/product/neo-7-series)
"2017-09-23" (https://www.eevblog.com/forum/testgear/new-gpsdo-bg7tbl/)
custom board with unknown OCXO. gps is unknown. compact design.
"2017-10-09" (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg1718495/#msg1718495)
custom board with surplus cts 970-2178 OCXO. gps is u-blox NEO-7M-0-000 (https://www.u-blox.com/en/product/neo-7-series)
"2017-12-16" (https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/202153437548)
custom board with unknown OCXO. gps is unknown. backlit LCD display.
"2019-09-23" (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg2457417/#msg2457417)
custom board with surplus bliley nvg47a1282 (http://web.archive.org/web/20160725005042/http://www.mikrocontroller.net/attachment/107430/6891__NVG47A1282_RoHS.pdf) OCXO. gps is unknown. compact design.
"2017-10-20" (https://www.eevblog.com/forum/testgear/new-gpsdo-bg7tbl/)
custom board with unknown OCXO. gps is unknown. backlit LCD display.
"GNSS-RB" (https://www.eevblog.com/forum/testgear/new-gpsdo-bg7tbl/)
GNSS disciplined Rubidium oscillator? gps is unknown. backlit LCD display.
construction quality of these devices is quite decent in general. the custom adapter models (oscilloquartz, trimble) of course have a number of bodge wires.
you get RS232, 1PPS and 10mhz outputs. wallwart PSU and active GPS antenna are included.
all in all, these are great value for the money and a lot less hassle than some of the alternative GPSDO options being thrown around on the forums. :-+
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"2014-11-06"
most extensively tested, so far (by ke5x and others).
known bug, output frequency is not exactly 10mhz (9,999,999.999800Hz). this translates to ~2hz error at 100ghz. ;D
http://www.ke5fx.com/gpscomp.htm (http://www.ke5fx.com/gpscomp.htm)
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"2014-12-09"
review by tim tuck / VK2XAX (https://drive.google.com/file/d/0B9Oysj7clpT7YTBWSjlfNTI1aTQ/view?usp=sharing)
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"2015-07-08"
surplus oscilloquartz gpsdo.
uses oscilloquartz star 4 (http://www.oscilloquartz.com/product-star-4-696-108) board.
bg7tbl "uccm board" dated 2015-06-27. appears identical to board used for the trimble.
rs232 interface is READ-ONLY. you cannot control the ublox with it, only monitor it.
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"2015-07-17"
surplus trimble gpsdo.
appears to use same "uccm board" as the 2015-07-17 (oscilloquartz) model.
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I supposedly have the 2014-12-9 on the way. Delivery times to Chile are horrible and I have waited 1-1/2 months so far. I will report all that I am capable of when it gets here.
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If you look closely at the unit with the Oscilloquartz board, it looks like he's attached a blue wire directly to the LEA-5T. That suggests that the comm port is just monitoring the GPS, not the GPSDO. You might not be able to control anything - just monitor.
Does anyone have one of these boards? Can you confirm or deny any of this?
Ed
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If you look closely at the unit with the Oscilloquartz board, it looks like he's attached a blue wire directly to the LEA-5T. That suggests that the comm port is just monitoring the GPS, not the GPSDO. You might not be able to control anything - just monitor.
Does anyone have one of these boards? Can you confirm or deny any of this?
Ed
Read Tim's teardown - it's not for the Oscilloquartz board, but it definitely seems the RS232 port is connected to the GPS.
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If you look closely at the unit with the Oscilloquartz board, it looks like he's attached a blue wire directly to the LEA-5T. That suggests that the comm port is just monitoring the GPS, not the GPSDO. You might not be able to control anything - just monitor.
Does anyone have one of these boards? Can you confirm or deny any of this?
Ed
Read Tim's teardown - it's not for the Oscilloquartz board, but it definitely seems the RS232 port is connected to the GPS.
I saw that. I don't have a problem with that. He designed it himself so I'm not expecting an intelligent controller. But I would be surprised if a commercial GPSDO didn't have some form of user access to the GPSDO functions.
Ed
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I saw that. I don't have a problem with that. He designed it himself so I'm not expecting an intelligent controller. But I would be surprised if a commercial GPSDO didn't have some form of user access to the GPSDO functions.
Ed
even if you could talk to the star 4 gpsdo, you would need the proprietary oscilloquartz configuration manager software. i couldn't find it anywhere.
you can buy surplus star 4 boards (http://www.168electronics.com/oscilloquartz-star4-osa-oem-gps-clock-p-122.html) if you want one to experiment on.
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I saw that. I don't have a problem with that. He designed it himself so I'm not expecting an intelligent controller. But I would be surprised if a commercial GPSDO didn't have some form of user access to the GPSDO functions.
Ed
even if you could talk to the star 4 gpsdo, you would need the proprietary oscilloquartz configuration manager software. i couldn't find it anywhere.
you can buy surplus star 4 boards (http://www.168electronics.com/oscilloquartz-star4-osa-oem-gps-clock-p-122.html) if you want one to experiment on.
Link doesn't work.
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I would be interested to see the performance of the Huawei Oscilloquartz model. It potentially has the best specced ocxo.
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I saw that. I don't have a problem with that. He designed it himself so I'm not expecting an intelligent controller. But I would be surprised if a commercial GPSDO didn't have some form of user access to the GPSDO functions.
Ed
even if you could talk to the star 4 gpsdo, you would need the proprietary oscilloquartz configuration manager software. i couldn't find it anywhere.
you can buy surplus star 4 boards (http://www.168electronics.com/oscilloquartz-star4-osa-oem-gps-clock-p-122.html) if you want one to experiment on.
Link doesn't work.
hmm maybe the domain owner forgot to pay his bill. lol.
https://web.archive.org/web/20150202061215/http://www.168electronics.com/oscilloquartz-star4-osa-oem-gps-clock-p-122.html (https://web.archive.org/web/20150202061215/http://www.168electronics.com/oscilloquartz-star4-osa-oem-gps-clock-p-122.html)
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I would be interested to see the performance of the Huawei Oscilloquartz model. It potentially has the best specced ocxo.
Which spec ? as far as I can tell its specs do not exceed those of the Morion.
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I got a BG7TBL 2014-12-09 unit { square wave out } , arrived yesterday { 1 week }. Inside is PCB marked 2015 with a Morion MV89 from 2007.
Initially unit did not lock, but traced it down to a shorted SMA cable from front panel to PCB. For now antenna direct connect to SMA on PCB. { Will fix front panel cable later }.
Seems to work ok now. GPS locked up in under 3 minutes. Longer term tests on-going.
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Thanks for creating this thread. It makes interesting reading and viewing.
I already own a couple of Trimble Thunderbolt GPSDO units with LCD display etc. but took an interest in these reasonably priced offerings from BG7TBL.
I would be interested to know more about BG7TBL. He creates some nice items and appears to be an interesting person to hear about.
Aurora
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Argh, you guys are a bad influence. That plus my inability to avoid impulse purchasing...
So I ordered a BG7TBL 2014-12-09 edition from eBay.
I already have a modified Lucent RFTGm-II-XO, with added 10MHz output via front panel BNC. This is the single-unit GPSDO (not the other half with the back-up Rubidium unit). It's nice and works well enough, but I haven't done a detailed evaluation of its performance. It is powered via an odd DB9 connector and you have to talk to it via RS-422 (which is fine for me since I have a couple of good USB to RS-422 adapters).
But I'm looking forward to a smaller, more modern unit that hopefully doesn't get as hot!
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I ordered and have received the BG7TBL "Trimble" unit. I have it set up and running now, but I'm going to let it stabilize for a few days before looking further.
Initial impressions: Much better GPS receiver than the Lucent, but not as good as I suspect the uBlox is. I wasn't able to get it to lock GPS inside the house where my test equipment is (same issue with teh Lucent). However, it locked up quickly on the other end of the house, and also when I put the antenna outside on the ground.
I compared the 10Mhz output to the Lucent this morning. They seem to be in sync, although the relative phase of the two signals drifts back and forth about 17 degrees over a relatively short time. I'll do some more quantitative measurements this weekend.
I really need a 3rd unit to see which unit has the phase drift. I suspect it's the Lucent, based on the crazy and constant adjustments its making to the EFC. Whoever wrote that code didn't know how to create a good PID loop.
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other than excellent sensitivity, the huawei/oscilloquartz star4 speaks both NMEA and UBLX. and the UBLX is very a well documented protocol.
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other than excellent sensitivity, the huawei/oscilloquartz star4 speaks both NMEA and UBLX. and the UBLX is very a well documented protocol.
So the serial port is connected to the UBlox (BPS) chip then? That doesn't allow for any status on the OCXO disciplining, things like EFC or HUD.
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other than excellent sensitivity, the huawei/oscilloquartz star4 speaks both NMEA and UBLX. and the UBLX is very a well documented protocol.
So the serial port is connected to the UBlox (BPS) chip then? That doesn't allow for any status on the OCXO disciplining, things like EFC or HUD.
without the proprietary oscilloquartz configuration manager software you wouldn't be able to talk to the ocxo anyway. the protocol does not appear to be documented. nor does the software appear to be available anymore.
nothing preventing anyone from modifying the bg7tbl huawei to connect rs232 to whatever chip on the board you want, if you want to try.
the 168electronics guy says star4 boards are available if someone wants to buy some.
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received my trimble unit, so now i have all three. lucent, oscilloquartz star4, and trimble.
trimble is marginally better than the lucent, but still pretty helpless with a puck antenna in a window with full view of the sky. the oscilloquartz star4 with the same antenna in the same location absolutely obliterates them both in terms of gps sensitivity and lock.
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received my trimble unit, so now i have all three. lucent, oscilloquartz star4, and trimble.
trimble is marginally better than the lucent, but still pretty helpless with a puck antenna in a window with full view of the sky. the oscilloquartz star4 with the same antenna in the same location absolutely obliterates them both in terms of gps sensitivity and lock.
The star4 is the same as the Huawei, right? I think it uses the ublox GPS, ao no surprise that it has better GPS sensitivity.
What about stability of the actual 10 MHz output?
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received my trimble unit, so now i have all three. lucent, oscilloquartz star4, and trimble.
trimble is marginally better than the lucent, but still pretty helpless with a puck antenna in a window with full view of the sky. the oscilloquartz star4 with the same antenna in the same location absolutely obliterates them both in terms of gps sensitivity and lock.
The star4 is the same as the Huawei, right? I think it uses the ublox GPS, ao no surprise that it has better GPS sensitivity.
What about stability of the actual 10 MHz output?
the "Huawei" bg7tbl is an oscilloquartz star4 board which uses oscilloquartz ocxo and ublox gps receiver.
stability is very good. I have yet to get the trimble to complete a survey due to poor receiver sensitivity, even putting the puck antenna outside didn't help (where it did with the lucent). I may have to get a timing antenna to make the lucent and trimble happy.
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I saw that. I don't have a problem with that. He designed it himself so I'm not expecting an intelligent controller. But I would be surprised if a commercial GPSDO didn't have some form of user access to the GPSDO functions.
Ed
even if you could talk to the star 4 gpsdo, you would need the proprietary oscilloquartz configuration manager software. i couldn't find it anywhere.
you can buy surplus star 4 boards (http://www.168electronics.com/oscilloquartz-star4-osa-oem-gps-clock-p-122.html) if you want one to experiment on.
Link doesn't work.
hmm maybe the domain owner forgot to pay his bill. lol.
https://web.archive.org/web/20150202061215/http://www.168electronics.com/oscilloquartz-star4-osa-oem-gps-clock-p-122.html (https://web.archive.org/web/20150202061215/http://www.168electronics.com/oscilloquartz-star4-osa-oem-gps-clock-p-122.html)
I just want to let everyone know not to waste their time with these guys at 168electronics. I emailed them for a price quote, thinking if I can reverse engineer the GPSDO interface that it might be worth making an adapter board and buying a batch to make available to folks. But "Bob Mokia" there told me they are not interested in selling ("Don't want to sell as I do some development on it"). Not sure why they have the thing listed on their web site.
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I emailed him, and never got a response back.
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I emailed him, and never got a response back.
Not surprised. He actually sent me a link to the eBay auction for the Huewai bg7tbl GPSDO.
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I had a couple of questions about the behavior I see with my Huawei – curious if others is the same:
1. In the upper right there is a window that has a field “fix mode”. Except for one time, when it briefly showed 2D/3D Fix, mine says “No Fix”. Also the satellite C/N window is always flashing on/off like it’s not locked or something. I notice if I connect u-center up to a unit with a NMEA output, this window does not flash.
2. I noticed that the u-center has a bunch of features to update state on the board, but although these options are all enabled, they don’t actually work. I opened up the board and discovered that only the TX pin is connected on the U-Blox chip – nothing is connected to the RX pin, so obviously the PC can’t talk back to the chip. It appears that everything is there for that to work if I just connect one wire, but I am suspicious why this was not already done. Is yours this way ?
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I had a couple of questions about the behavior I see with my Huawei – curious if others is the same:
1. In the upper right there is a window that has a field “fix mode”. Except for one time, when it briefly showed 2D/3D Fix, mine says “No Fix”. Also the satellite C/N window is always flashing on/off like it’s not locked or something. I notice if I connect u-center up to a unit with a NMEA output, this window does not flash.
2. I noticed that the u-center has a bunch of features to update state on the board, but although these options are all enabled, they don’t actually work. I opened up the board and discovered that only the TX pin is connected on the U-Blox chip – nothing is connected to the RX pin, so obviously the PC can’t talk back to the chip. It appears that everything is there for that to work if I just connect one wire, but I am suspicious why this was not already done. Is yours this way ?
I don't have this board, but I suspect that if you monitored the Rx pin with a scope, you'd find that there's already data on it coming from the on-board processor. Since BG7TBL couldn't figure out how to talk to the processor, he decided to eavesdrop on the data coming from the LEA-5T. This is the same thing that the Lucent pair do.
Maybe u-center doesn't like being in a passive monitoring mode or is confused as to the current state of the LEA-5T. If you could have u-center send the correct commands (even though they don't get to the LEA-5T), then at least u-center and the LEA-5T were in the same state.
Ed
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Just for the 5t, try hooking up two wires to the usb pin( the 6 has one).
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I have received my 2014-09-12 a couple of days ago, and I will be setting it up the next couple of days. I want to use this for both a frequency standard to turn a computer into a local time server.Any ideas which is a decent software to do this with this device? I found this:
http://www.visualgps.net/nmeatime/ (http://www.visualgps.net/nmeatime/)
Any thoughts?
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I have received my 2014-09-12 a couple of days ago, and I will be setting it up the next couple of days. I want to use this for both a frequency standard to turn a computer into a local time server.Any ideas which is a decent software to do this with this device? I found this:
http://www.visualgps.net/nmeatime/ (http://www.visualgps.net/nmeatime/)
Any thoughts?
Nmeatime will keep the clock on your PC correct. If you want to use it to keep other PCs correct, you need an NTP server. There are many different ones - some free, some not. Google is your friend, but here are a few:
https://www.meinbergglobal.com/english/sw/ntp.htm (https://www.meinbergglobal.com/english/sw/ntp.htm)
http://www.ntp.org/ (http://www.ntp.org/)
Looks like Windows 7 might have NTP server capabilities. I haven't investigated it.
https://social.technet.microsoft.com/Forums/windowsserver/en-US/ffb1df0b-7c6e-4b2d-8fdf-b4ca0c014266/configuring-windows-7-as-an-ntp-server (https://social.technet.microsoft.com/Forums/windowsserver/en-US/ffb1df0b-7c6e-4b2d-8fdf-b4ca0c014266/configuring-windows-7-as-an-ntp-server)
Ed
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Just for the 5t, try hooking up two wires to the usb pin( the 6 has one).
I don't understand. Can you explain in more detail?
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I had a couple of questions about the behavior I see with my Huawei – curious if others is the same:
1. In the upper right there is a window that has a field “fix mode”. Except for one time, when it briefly showed 2D/3D Fix, mine says “No Fix”. Also the satellite C/N window is always flashing on/off like it’s not locked or something. I notice if I connect u-center up to a unit with a NMEA output, this window does not flash.
2. I noticed that the u-center has a bunch of features to update state on the board, but although these options are all enabled, they don’t actually work. I opened up the board and discovered that only the TX pin is connected on the U-Blox chip – nothing is connected to the RX pin, so obviously the PC can’t talk back to the chip. It appears that everything is there for that to work if I just connect one wire, but I am suspicious why this was not already done. Is yours this way ?
I don't have this board, but I suspect that if you monitored the Rx pin with a scope, you'd find that there's already data on it coming from the on-board processor. Since BG7TBL couldn't figure out how to talk to the processor, he decided to eavesdrop on the data coming from the LEA-5T. This is the same thing that the Lucent pair do.
Maybe u-center doesn't like being in a passive monitoring mode or is confused as to the current state of the LEA-5T. If you could have u-center send the correct commands (even though they don't get to the LEA-5T), then at least u-center and the LEA-5T were in the same state.
Ed
Oh yes, of course! I didn't even think about that, but it's obvious in retrospect.
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I had a couple of questions about the behavior I see with my Huawei – curious if others is the same:
1. In the upper right there is a window that has a field “fix mode”. Except for one time, when it briefly showed 2D/3D Fix, mine says “No Fix”. Also the satellite C/N window is always flashing on/off like it’s not locked or something. I notice if I connect u-center up to a unit with a NMEA output, this window does not flash.
2. I noticed that the u-center has a bunch of features to update state on the board, but although these options are all enabled, they don’t actually work. I opened up the board and discovered that only the TX pin is connected on the U-Blox chip – nothing is connected to the RX pin, so obviously the PC can’t talk back to the chip. It appears that everything is there for that to work if I just connect one wire, but I am suspicious why this was not already done. Is yours this way ?
I don't have this board, but I suspect that if you monitored the Rx pin with a scope, you'd find that there's already data on it coming from the on-board processor. Since BG7TBL couldn't figure out how to talk to the processor, he decided to eavesdrop on the data coming from the LEA-5T. This is the same thing that the Lucent pair do.
Maybe u-center doesn't like being in a passive monitoring mode or is confused as to the current state of the LEA-5T. If you could have u-center send the correct commands (even though they don't get to the LEA-5T), then at least u-center and the LEA-5T were in the same state.
Ed
Oh yes, of course! I didn't even think about that, but it's obvious in retrospect.
connected my huawei bg7tbl to the scope and probed rxd. it does seem like the processor is sending data to the lea-5t. but it's only always the same thing, once a second.
0xB5 0x62 0x0B 0x02 0x00 0x00 0x0D 0x32
in UBX protocol this translates to an AID-HUI poll request (Poll GPS Health, UTC and ionosphere parameters).
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connected my huawei bg7tbl to the scope and probed rxd. it does seem like the processor is sending data to the lea-5t. but it's only always the same thing, once a second.
0xB5 0x62 0x0B 0x02 0x00 0x00 0x0D 0x32
in UBX protocol this translates to an AID-HUI poll request (Poll GPS Health, UTC and ionosphere parameters).
It's not surprising that the same requests are made over and over. There might be some different commands sent just after powerup to set the LEA-5T into the proper mode to provide the info that u-center wants. I'm not familiar with the u-blox modules, but some possibilities that come to mind are things like:
- binary vs. NMEA output
- mask angle
- UTC vs GPS time
- provide data output automatically or only on request
- 1 PPS output all the time or only when locked
There could be many others.
Ed
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OK, my bg7tbl 2014-09-12 is running, locked and refining. I have run NMEATime and it is working but..
NMEATime only does clock updates only every 1 minute. It also doesn't indicate whether the 1PPS is actually being read. So, I need/want a clock tracking software that actually updates closer to every 10 seconds, and indicates whether it actually sees the 1PPS signal. Then after that I need to get the NTP service running. Any suggestions?
So I have a rubidium standard that seems to agree (within a few tenths of PPM with my capability so far) with the bg7tbl so far but I will see after the bg7tbl settles in. Of course the rubidium standard is old and could have drifted I assume. Either it seems I have two references that agree within 0.1PPM at least. I am happy.
My bg7tbl locked GPS within 10 minutes, and the warning LED turned off after around 20 minutes. Sorry, I didn't time it.
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OK, my bg7tbl 2014-09-12 is running, locked and refining. I have run NMEATime and it is working but..
NMEATime only does clock updates only every 1 minute. It also doesn't indicate whether the 1PPS is actually being read. So, I need/want a clock tracking software that actually updates closer to every 10 seconds, and indicates whether it actually sees the 1PPS signal. Then after that I need to get the NTP service running. Any suggestions?
Yeah... don't waste your time on other s/w, implement NTP directly since it will accept PPS input and give you a stratum 1 clock.
A good "how too" is here...
http://www.satsignal.eu/ntp/Sure-GPS.htm (http://www.satsignal.eu/ntp/Sure-GPS.htm)
While it uses the SureGPS dev board it can be applied to any GPS with PPS/NMEA output.
So I have a rubidium standard that seems to agree (within a few tenths of PPM with my capability so far) with the bg7tbl so far but I will see after the bg7tbl settles in. Of course the rubidium standard is old and could have drifted I assume. Either it seems I have two references that agree within 0.1PPM at least. I am happy.
LOL.... A man with two clocks never knows what time it is - you need 3 or more to have some certainty!
Once the GPSDO settles in, it will be the most accurate source and you could cal your RB against that.
regards
Tim
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Hopefullly they will stay in stock until Christmas. Currently e-mailling oscilloquartz about the star 4 module.
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Yeah... don't waste your time on other s/w, implement NTP directly since it will accept PPS input and give you a stratum 1 clock.
A good "how too" is here...
http://www.satsignal.eu/ntp/Sure-GPS.htm (http://www.satsignal.eu/ntp/Sure-GPS.htm)
While it uses the SureGPS dev board it can be applied to any GPS with PPS/NMEA output.
Thanks for the link. I am not very sure how I can implement the idea in that link for me. It seems to be specific to a certain USB-232 converter chip which I don't have.
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Thanks for the link. I am not very sure how I can implement the idea in that link for me. It seems to be specific to a certain USB-232 converter chip which I don't have.
OK - then the question is do you have a serial port ? if yes then PPS in to NTP over the DCD pin.
If not then, you can use a USB to Serial adapter to do this.
The same web site has a discussion about this on a separate page here...
http://www.satsignal.eu/ntp/NTP-on-Windows-serial-port.html (http://www.satsignal.eu/ntp/NTP-on-Windows-serial-port.html)
under the heading "Using a Serial - USB converter"
regards
Tim
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Thanks again. Like I said I wasn't sure how to do it yet. There is lots to wade through on that web site.
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My 2014-09-12 has been running for a day now. I fired up my rubidium standard and let stabilize for over an hour and then measured the phase drift between the two.
The first appearance was that they perfectly matched! But it was not so. I could see a small drift, so I measured it. It appears that my rubidium standard leads the bg7tbl by 5ns per 80 seconds. I need to figure out how to do the math of the actual frequency difference, but from this it is really low.
I am still working on getting the best time server accuracy going, but that will take some reading.
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My 2014-09-12 has been running for a day now. I fired up my rubidium standard and let stabilize for over an hour and then measured the phase drift between the two.
The first appearance was that they perfectly matched! But it was not so. I could see a small drift, so I measured it. It appears that my rubidium standard leads the bg7tbl by 5ns per 80 seconds. I need to figure out how to do the math of the actual frequency difference, but from this it is really low.
I am still working on getting the best time server accuracy going, but that will take some reading.
Give it some time. I know have 4 different units here (will definitely be selling at least 2 of them if anyone is interested): Lucent, BG7TBL/Trimble/2015-07-17, BG7TBL/Huawei/2015-07-08, and BG7TBL/2014-12-09 (Morion/UBlox). Initially it looked to me like the 2014-12-09 was off in frequency, but after letting it settle for a few days, it seems to behave like the others but with a little more variance. They all drift relative to each other anywhere from 5 - 9ns, and then reverse and drift back in the other direction (so totally relative difference < 18ns).
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I was pretty sure that I needed to wait a few more days, and to also let the rubidium standard stabilize for a longer time too. I was just pleased at how low the difference was already. What is the math to figure out the frequency difference? I am too lazy right now to figure it out. :D
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With multiple GPSDO's you will need to check their specs sheets to see which is the best.
i.e. the uBLox based units are/where using the NEO-6 GPS unit. This has a PPS accuracy specified at 30ns RMS, its timing brother the T version can achieve 15ns.
All GPSDO's specs assume a "full sky view" i.e. they can see as many sats as possible to achieve these specs. Each GPS sat has Cesium Standards on board that are synced to hydrogen masers back in the US and with units like the uBLox that can see GLONAS, there is additional frames of reference from Russia. So the more "clocks" in view the more accurate your output will be.
So.... the thing to do is to find out which is the highest spec GPSDO you have and make that the base reference by which all others are compared. It will also probably take a week or so for everything to settle down.
regards
Tim
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Well I have an unobstructed all sky view for my antenna, no problem there. I ave only one GPSDO. I thought that would be enough as I don't need another obsession. The FE5680B is the only other real standard I have. My biggest problem is big temperature swings where my equipment is. Anywhere from 0°C winter night to 40°C summer day. I am trying to get this under control. Daily variations tend to be in the 25°C range.
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I was pretty sure that I needed to wait a few more days, and to also let the rubidium standard stabilize for a longer time too. I was just pleased at how low the difference was already. What is the math to figure out the frequency difference? I am too lazy right now to figure it out. :D
Well, I am certainly new to this area and not an expert, but I think there shouldn't be a frequency difference once it's locked. I would expect it would vary by some fraction of a full period, but the GPS-driven adjustments should bring it back. That seems to be what I am seeing, but I am not viewing it over a very long time.
If there is a frequency difference, it will "slip" N cycles over some period of time, T relative to the reference. The frequency difference is N/T. So for example, if you hooked source 1 up to a counter and incremented that counter every cycle, and hook source 2 up to another counter and increment it every cycle, and after 1000 seconds of observation the two counters differed by 2 counts, then the frequency difference would be 2/1000 = 0.002 Hz.
(Adding fractional cycles)
If it's slipping a fraction of a cycle, just plug that in - so 5ns is 0.05 of the 100ns period of a 10 MHz source, so 5ns in 80 seconds is 0.05 / 80 = 0.000625 Hz
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Well I have an unobstructed all sky view for my antenna, no problem there. I ave only one GPSDO. I thought that would be enough as I don't need another obsession. The FE5680B is the only other real standard I have. My biggest problem is big temperature swings where my equipment is. Anywhere from 0°C winter night to 40°C summer day. I am trying to get this under control. Daily variations tend to be in the 25°C range.
I certainly don't need more than one myself, but obsessions seem to come easy :)
That is a big temperature swing.
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Based on what what I can calculate in my clouded head right now. 5nS per 80S is 3.75nS per minute, 6.25-11 every second, or 1600 seconds per cycle at 10MHz, or 0.000625 Hz difference? 6.25-9% difference? If so, it would be hard for me to improve the adjustment of the rubidium standard!
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Based on what what I can calculate in my clouded head right now. 5nS per 80S is 3.75nS per minute, 6.25-11 every second, or 1600 seconds per cycle at 10MHz, or 0.000625 Hz difference? 6.25-9% difference? If so, it would be hard for me to improve the adjustment of the rubidium standard!
I don't think that's valid. This assumes that it's going to continue, linearly, to drift 5ns every 80s. For the GPSDO, the GPS adjusts the value and they start to drift back in the other direction.
Oh, but I guess you're talking about a Rubidium standard here, which isn't GPS disciplined.
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The FE5680 will slow drift off over time, but a very long time. The nice thing about them is that you can turn them off and when you turn them back on it only takes 5 minutes to achieve an accurate lock. GPSDO's will take much longer to settle and are best when not turned off at all.
The FE5680 is also adjustable in tiny increments, a quote from the manual for mine...
"The FE-5680A output frequency can be adjusted digitally over the RS-232 interface (pins
8 and 9). This feature is available as option 2, and is not available on units purchased
without this option. The frequency can be adjusted with a resolution of 1.7854E-7 Hz. For
an FE-5680A device with an output frequency of 10 MHz, this corresponds to a relative
frequency setting resolution of 1.7854E-14."
If you're lucky enough to have a unit with option 2 in it of course :)
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Well I have an unobstructed all sky view for my antenna, no problem there. I ave only one GPSDO. I thought that would be enough as I don't need another obsession. The FE5680B is the only other real standard I have. My biggest problem is big temperature swings where my equipment is. Anywhere from 0°C winter night to 40°C summer day. I am trying to get this under control. Daily variations tend to be in the 25°C range.
Like all Rb standards, the Fe5680B will change frequency slightly due to temperature changes. You can minimize this with fairly trivial effort. Just putting it in a cardboard box will reduce the changes significantly. For a slightly more professional version, put the 5680B in an enclosure with a temperature-controlled fan that draws outside air through the enclosure.
Ed
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The FE5680 will slow drift off over time, but a very long time. The nice thing about them is that you can turn them off and when you turn them back on it only takes 5 minutes to achieve an accurate lock. GPSDO's will take much longer to settle and are best when not turned off at all.
The FE5680 is also adjustable in tiny increments, a quote from the manual for mine...
"The FE-5680A output frequency can be adjusted digitally over the RS-232 interface (pins
8 and 9). This feature is available as option 2, and is not available on units purchased
without this option. The frequency can be adjusted with a resolution of 1.7854E-7 Hz. For
an FE-5680A device with an output frequency of 10 MHz, this corresponds to a relative
frequency setting resolution of 1.7854E-14."
If you're lucky enough to have a unit with option 2 in it of course :)
I don't know about the 'B' version, but some versions of the 5680A also have a screwdriver adjust for really fine frequency adjustment.
Ed
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My point was that the error, based on the current state of affairs, was far below my ability to adjust it. The FE5680B is a bit of a different beast from the A series. If I need better accuracy, I should move to a climate controlled air tight laboratory. >:D
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Hopefullly they will stay in stock until Christmas. Currently e-mailling oscilloquartz about the star 4 module.
I emailed them as well. 8)
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I set the frequency counter up to calculate the ratio of the two frequency inputs. I set the gate time to the maximum value, which is 1000 seconds. Using the Lucent as input one, I hooked up the three BG7TBL units up successively to the frequency two input.
The ratio for the BG7TBL/TRIMBLE and BG7TBL/Huawei(Oscilloquartz Star4) was consistently 1.000.000.000.0. I ran each for a number of 1000 second cycles with stats turned on and tracking the max/min values, and I never saw any other value. The BG7TBL/2014-12-09, on the other hand, gave me some 1.0 readings, but there were a couple of 1.000.000.000.1 readings. I believe this is because the bug with the frequency being slightly off is still there. In any event, for most people I think it's a non issue. I can only barely see the problem at the limits of my counter.
Of all 4 units, I like both the Lucent and the Huawei/Oscilloquartz/Star4. I love that the Lucent has a serial interface where you can send commands and view stats. The Huawei/Oscilloquartz/Star4 has only a read-only, GPS-only interface, but it has a GPS chip with better sensitivity and more channels, a very good, cooler-running OCXO, is more compact, devoid of strange power connectors, and has a clean sine wave output. If we can get some sort of read/write interface working for the Huawei/Oscilloquartz/Star4, it would be a hands-down winner.
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I set the frequency counter up to calculate the ratio of the two frequency inputs. I set the gate time to the maximum value, which is 1000 seconds. Using the Lucent as input one, I hooked up the three BG7TBL units up successively to the frequency two input.
The ratio for the BG7TBL/TRIMBLE and BG7TBL/Huawei(Oscilloquartz Star4) was consistently 1.000.000.000.0. I ran each for a number of 1000 second cycles with stats turned on and tracking the max/min values, and I never saw any other value. The BG7TBL/2014-12-09, on the other hand, gave me some 1.0 readings, but there were a couple of 1.000.000.000.1 readings. I believe this is because the bug with the frequency being slightly off is still there. In any event, for most people I think it's a non issue. I can only barely see the problem at the limits of my counter.
Of all 4 units, I like both the Lucent and the Huawei/Oscilloquartz/Star4. I love that the Lucent has a serial interface where you can send commands and view stats. The Huawei/Oscilloquartz/Star4 has only a read-only, GPS-only interface, but it has a GPS chip with better sensitivity and more channels, a very good, cooler-running OCXO, is more compact, devoid of strange power connectors, and has a clean sine wave output. If we can get some sort of read/write interface working for the Huawei/Oscilloquartz/Star4, it would be a hands-down winner.
Since you have a 53131A counter, why not measure the time interval from the rising edge on the Lucent to the rising edge on one of the others. This is the highest resolution method of directly comparing two oscillators. Collect the data via RS-232 with Timelab. Frequency offsets like the bug in the BG7TBL unit will be easy to see rather than digging around in the last digit. Some of your results won't be as good as John Miles' when he discovered the bug because his equipment is so much better than ours, but some of it will be comparable.
Ed
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With multiple GPSDO's you will need to check their specs sheets to see which is the best.
i.e. the uBLox based units are/where using the NEO-6 GPS unit. This has a PPS accuracy specified at 30ns RMS, its timing brother the T version can achieve 15ns.
the bg7tbl star4 gpsdo uses the ublox LEA-5T unit.
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I set the frequency counter up to calculate the ratio of the two frequency inputs. I set the gate time to the maximum value, which is 1000 seconds. Using the Lucent as input one, I hooked up the three BG7TBL units up successively to the frequency two input.
The ratio for the BG7TBL/TRIMBLE and BG7TBL/Huawei(Oscilloquartz Star4) was consistently 1.000.000.000.0. I ran each for a number of 1000 second cycles with stats turned on and tracking the max/min values, and I never saw any other value. The BG7TBL/2014-12-09, on the other hand, gave me some 1.0 readings, but there were a couple of 1.000.000.000.1 readings. I believe this is because the bug with the frequency being slightly off is still there. In any event, for most people I think it's a non issue. I can only barely see the problem at the limits of my counter.
Of all 4 units, I like both the Lucent and the Huawei/Oscilloquartz/Star4. I love that the Lucent has a serial interface where you can send commands and view stats. The Huawei/Oscilloquartz/Star4 has only a read-only, GPS-only interface, but it has a GPS chip with better sensitivity and more channels, a very good, cooler-running OCXO, is more compact, devoid of strange power connectors, and has a clean sine wave output. If we can get some sort of read/write interface working for the Huawei/Oscilloquartz/Star4, it would be a hands-down winner.
Since you have a 53131A counter, why not measure the time interval from the rising edge on the Lucent to the rising edge on one of the others. This is the highest resolution method of directly comparing two oscillators. Collect the data via RS-232 with Timelab. Frequency offsets like the bug in the BG7TBL unit will be easy to see rather than digging around in the last digit. Some of your results won't be as good as John Miles' when he discovered the bug because his equipment is so much better than ours, but some of it will be comparable.
Ed
I don't have the data logging set up yet, but I can combine the TI measurement with the built-in stats calculation on the 53131A.
Not sure I have this right - 53131A is not known for its intuitive UI. I set it up for "TI 1 to 2" measurement, then enabled Statistics with 1000 samples and ran a single stats cycle. Both channels have 50 ohm termination, AC coupling, auto trigger levels.
(All values in microseconds unless otherwise noted)
Lucent to Huawei - StdDev 0.000590; Mean 0.091113; Max 0.0923; Min 0.0898 -> (max - min) = 2.5 ns
Lucent to Trimble - StdDev 0.000355; Mean 0.047302; Max 0.0488; Min 0.0463 -> (max-min) = 2.5 ns
Lucent to BG7TBL - StdDev 0.000356; Mean 0.095016; Max 0.0958; Min 0.0943 -> (max-min) = 1.5 ns
Trimble to Huawei - StdDev 0.000685; Mean 0.050237; Max 0.0523; Min 0.0488 -> (max-min) = 3.5 ns
Trimble to BG7TBL - StdDev 0.000615; Mean 0.050347; Max 0.0523; Min 0.0493 -> (max-min) = 3.0 ns
Huwaei to BG7TBL - StdDev 0.000952; Mean 0.018382; Max 0.0213; Min 0.0163 -> (max-min) = 5.0 ns
I might have upset things a bit by jostling the GPSDO enclosures. It's hard to plug/unplug BNCs on these things. I will let them sit for awhile and repeat one of the measurements to see how much it changes. Might also make sense to do a longer sample run - maybe 10,000 samples.
(edit) More samples on Huawei to BG7TGBL - StdDev 0.010116; Mean 0.0355101; Max 0.0523; Min 0.0203 -> (max-min) = 32 ns
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I don't have the data logging set up yet, but I can combine the TI measurement with the built-in stats calculation on the 53131A.
Not sure I have this right - 53131A is not known for its intuitive UI. I set it up for "TI 1 to 2" measurement, then enabled Statistics with 1000 samples and ran a single stats cycle. Both channels have 50 ohm termination, AC coupling, auto trigger levels.
(All values in microseconds unless otherwise noted)
Lucent to Huawei - StdDev 0.000590; Mean 0.091113; Max 0.0923; Min 0.0898 -> (max - min) = 2.5 ns
Lucent to Trimble - StdDev 0.000355; Mean 0.047302; Max 0.0488; Min 0.0463 -> (max-min) = 2.5 ns
Lucent to BG7TBL - StdDev 0.000356; Mean 0.095016; Max 0.0958; Min 0.0943 -> (max-min) = 1.5 ns
Trimble to Huawei - StdDev 0.000685; Mean 0.050237; Max 0.0523; Min 0.0488 -> (max-min) = 3.5 ns
Trimble to BG7TBL - StdDev 0.000615; Mean 0.050347; Max 0.0523; Min 0.0493 -> (max-min) = 3.0 ns
Huwaei to BG7TBL - StdDev 0.000952; Mean 0.018382; Max 0.0213; Min 0.0163 -> (max-min) = 5.0 ns
I might have upset things a bit by jostling the GPSDO enclosures. It's hard to plug/unplug BNCs on these things. I will let them sit for awhile and repeat one of the measurements to see how much it changes. Might also make sense to do a longer sample run - maybe 10,000 samples.
(edit) More samples on Huawei to BG7TGBL - StdDev 0.010116; Mean 0.0355101; Max 0.0523; Min 0.0203 -> (max-min) = 32 ns
This is useful information. It shows that all the units appear to be working properly. For most users, any of them would provide excellent service.
Now, can we answer the question: Which one of these units is the best? Moto, in the unlikely case that you haven't figured it out yet, I'm playing to the audience here! ;)
The mean, max, and min values are arbitrary so they aren't useful. Every test will give different values.
The Std. Dev. and Max-Min values are very useful. You would expect those values to be similar (but not equal) from one test to another. The two lowest Std. Dev. values both include the Lucent which suggests that it's the best one. The Max-Min values are also at the low end of the scale. The Trimble measurements are in the middle. Huawei comes next. But the BG7TBL measurements are both the best and worst of the pack! :o
No, nothing's wrong. These results aren't surprising. GPS signals have jitter, so anytime you take a snapshot you could get a really good result or a not-so-good result. Your edit clearly shows the affect of a not-so-good snapshot. That one justifies the term 'outlier'. We pretend that those measurements never happened. Seriously, that's allowed! Something hiccupped and the data is trash so you discard it.
To get some useful results out of these measurements, you have to take multiple data runs and compare the results to determine what typical results are.
Regarding the data logging, I urge you to get that going. Timelab handles both the data collection and analysis. All you have to do is plug in the cable! Well, okay, you have to configure the serial port. And I guess you have to figure out which cable wiring you need. But you can handle that! :D Logging the data will move you out of the 'snapshot' business. You'll be able to see how the units perform over time and your comparisons will be more consistent. You should be able to confirm the frequency error of the BG7TBL unit - unless he's come out with a new firmware version that fixes the problem. That would be interesting news!
If you look back at this message (https://www.eevblog.com/forum/testgear/economical-option-for-precision-frequency-reference/msg712741/#msg712741), it shows some of the things that Timelab can tell you about these units. Yeah yeah, I know tl;dr, and even when you try and read it your eyes glaze over. What can I say? If you were trying to measure the diameter of a metal shaft, would you use a plastic ruler or learn how to use a micrometer?
Ed
P.S. Do I dare mention that the best way to evaluate a GPSDO is to compare it to a local standard like a Rubidium oscillator? ;)
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P.S. Do I dare mention that the best way to evaluate a GPSDO is to compare it to a local standard like a Rubidium oscillator? ;)
And on that note!
Day three with my bg7tbl and I did some more time checking the frequency difference. Yesterday the drift was 3.75nS per second between my bg7tbl and my FE5680B. This indicated the FE5680B was lower by around 0.000625Hz. Today the drift was around 3nS per second. This would imply 0.0005Hz.
Which is correct? I don't know. Maybe they will get closer as time as goes on.
What else can I characterize with a oscilloscope, a used FE5680B, and a computer?
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I don't have the data logging set up yet, but I can combine the TI measurement with the built-in stats calculation on the 53131A.
Not sure I have this right - 53131A is not known for its intuitive UI. I set it up for "TI 1 to 2" measurement, then enabled Statistics with 1000 samples and ran a single stats cycle. Both channels have 50 ohm termination, AC coupling, auto trigger levels.
(All values in microseconds unless otherwise noted)
Good to see some data, and given you're now measuring into the nS other thing need to be taken into account.
Are the leads from each GPS to the counter, the same length ?
Are they sharing a common antenna and, if you're using a splitter to share that antenna, are those leads also the same length ?
Are those patch leads made of the same material since velocity factor of the cable will also contribute.
When measuring such short time intervals it is important to remember that 1nS =11.8" or 29.98cm dependent on your unit of measure.
Disparate lead length will contribute nS or fractional nS offsets as will operating the GPS's at different heights since we're also now into the realm of relativistic effects. ( Dave demonstrated that in one of his videos )
A common antenna is critical to ensure multi path effects and other external influences are common too.
Other factors can contribute to GPS error, the Thunderbolt Manual is a wealth of information and contains a table that has these effects to consider...
Error Source --- 1 Standard Deviation
Atmospheric Models (Ionosphere) --- 5 - 50 ns
Receiver noise (Multipath) --- 1 - 20 ns
Satellite Clock Model --- 10 ns
Satellite Orbit Model --- 5 ns
Antenna Survey --- 1 ns
+1 to edpalmer for mentioning TimeLab - this software is specifically designed for such measurements.
Comparison of these devices can lead to frustration when you are unsure of which source is the "truth" and nearly everything you set up to get data contributes to the error of the result.
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P.S. Do I dare mention that the best way to evaluate a GPSDO is to compare it to a local standard like a Rubidium oscillator? ;)
And on that note!
Day three with my bg7tbl and I did some more time checking the frequency difference. Yesterday the drift was 3.75nS per second between my bg7tbl and my FE5680B. This indicated the FE5680B was lower by around 0.000625Hz. Today the drift was around 3nS per second. This would imply 0.0005Hz.
Which is correct? I don't know. Maybe they will get closer as time as goes on.
What else can I characterize with a oscilloscope, a used FE5680B, and a computer?
Both values are correct. They are 'snapshots' as I described in my previous message to motocoder. Don't think in terms of 'ns per second'. Measure the offset and note the time. From there, keep recording the offset and time over a period of hours. When you graph it, you'll see the short-term wiggles as well as the long-term trend (if any). If the trend is a straight line, everything is good. The slope of the straight line shows the frequency offset. If you want, you can tweak the frequency of your FE5680B to reduce the offset. If it's curving around, you'll have to look deeper to see what's happening.
Exactly what are you measuring - offset between two 1 PPS signals or 1 PPS vs. 10 MHz? If you're using the 10 MHz, you should probably divide it down to a lower frequency so that the phase doesn't wrap while you're taking measurments. That creates headaches when it comes to analyzing the data.
Ed
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I am measuring the phase change of the 10MHz signals. I don't have the time to do many measurements during the day right now. I am just checking it daily. But I will probably do as you suggest in a week or so. I was rather surprised at how close they are given that my FE5680B must be rather old and I thought it might have drifted a bit.
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I don't have the data logging set up yet, but I can combine the TI measurement with the built-in stats calculation on the 53131A.
Not sure I have this right - 53131A is not known for its intuitive UI. I set it up for "TI 1 to 2" measurement, then enabled Statistics with 1000 samples and ran a single stats cycle. Both channels have 50 ohm termination, AC coupling, auto trigger levels.
(All values in microseconds unless otherwise noted)
Good to see some data, and given you're now measuring into the nS other thing need to be taken into account.
Are the leads from each GPS to the counter, the same length ?
Are they sharing a common antenna and, if you're using a splitter to share that antenna, are those leads also the same length ?
Are those patch leads made of the same material since velocity factor of the cable will also contribute.
When measuring such short time intervals it is important to remember that 1nS =11.8" or 29.98cm dependent on your unit of measure.
Disparate lead length will contribute nS or fractional nS offsets as will operating the GPS's at different heights since we're also now into the realm of relativistic effects. ( Dave demonstrated that in one of his videos )
A common antenna is critical to ensure multi path effects and other external influences are common too.
Other factors can contribute to GPS error, the Thunderbolt Manual is a wealth of information and contains a table that has these effects to consider...
Error Source --- 1 Standard Deviation
Atmospheric Models (Ionosphere) --- 5 - 50 ns
Receiver noise (Multipath) --- 1 - 20 ns
Satellite Clock Model --- 10 ns
Satellite Orbit Model --- 5 ns
Antenna Survey --- 1 ns
+1 to edpalmer for mentioning TimeLab - this software is specifically designed for such measurements.
Comparison of these devices can lead to frustration when you are unsure of which source is the "truth" and nearly everything you set up to get data contributes to the error of the result.
Variations in lead length and velocity factor don't affect these kinds of measurements. They create a constant offset which is tossed out with the mean, max, and min values. They could be significant if you were trying to synchronize your 1 PPS signal to a real world time of day signal or some other existing standard.
Antenna issues however, are something to think about. Differences in antenna gain and receiver sensitivity could change the results. If there's any RF interference, different antennas will do a better or worse job of filtering that. How will each receiver react to that? It would be interesting to gather enough data to establish some level of confidence in the results and then swap the antennas and see if the results change.
Ed
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I don't have the data logging set up yet, but I can combine the TI measurement with the built-in stats calculation on the 53131A.
Not sure I have this right - 53131A is not known for its intuitive UI. I set it up for "TI 1 to 2" measurement, then enabled Statistics with 1000 samples and ran a single stats cycle. Both channels have 50 ohm termination, AC coupling, auto trigger levels.
(All values in microseconds unless otherwise noted)
Good to see some data, and given you're now measuring into the nS other thing need to be taken into account.
Are the leads from each GPS to the counter, the same length ?
Are they sharing a common antenna and, if you're using a splitter to share that antenna, are those leads also the same length ?
Are those patch leads made of the same material since velocity factor of the cable will also contribute.
When measuring such short time intervals it is important to remember that 1nS =11.8" or 29.98cm dependent on your unit of measure.
Disparate lead length will contribute nS or fractional nS offsets as will operating the GPS's at different heights since we're also now into the realm of relativistic effects. ( Dave demonstrated that in one of his videos )
A common antenna is critical to ensure multi path effects and other external influences are common too.
Other factors can contribute to GPS error, the Thunderbolt Manual is a wealth of information and contains a table that has these effects to consider...
Error Source --- 1 Standard Deviation
Atmospheric Models (Ionosphere) --- 5 - 50 ns
Receiver noise (Multipath) --- 1 - 20 ns
Satellite Clock Model --- 10 ns
Satellite Orbit Model --- 5 ns
Antenna Survey --- 1 ns
+1 to edpalmer for mentioning TimeLab - this software is specifically designed for such measurements.
Comparison of these devices can lead to frustration when you are unsure of which source is the "truth" and nearly everything you set up to get data contributes to the error of the result.
I agree with Ed's reply to your post, but just want to clarify one thing. Those variables you point out impact only those values that represent absolutes, i.e. not deltas between samples. So coax cable length differences (and by the way, the lengths are identical) do impact the mean, max, and minimum value. I pointed this out when I mentioned that each unit has a potentially different value for the antenna delay constant (something you left out of your list). From what I have read, this value is used to adjust the time offset to compensate for propagation time between the antenna and the GPS.
However, as Ed points out, these variables do NOT impact the relative measurements that I provided, i.e. the standard deviation and the span (max - min) values. And that's really the only thing I'm interested in with these measurements - I just posted them because I had the data and thought people might want to see it.
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I bumped up the count on the 53131A statistics. The UI on this thing baffles me sometimes, but I think it ran for about 45 minutes or so before emitting a value.
Lucent to BG7TBL/2014-12-09 - StdDev 3.4090ns, Max 48.8ns, Min 35.3ns, (Max-Min) 13.5ns.
This value correlates well with what I've seen by hooking my scope up to trigger on the Lucent, setting the BG7TBL up on the other channel with infinite persistence, and then measuring the horizontal deviation of the two waveforms. Is this an indication that this version of the BG7TBL does not have the slightly off frequency issue?
I will see if I can get TimeLab up and running next.
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I bumped up the count on the 53131A statistics. The UI on this thing baffles me sometimes, but I think it ran for about 45 minutes or so before emitting a value.
Lucent to BG7TBL/2014-12-09 - StdDev 3.4090ns, Max 48.8ns, Min 35.3ns, (Max-Min) 13.5ns.
This value correlates well with what I've seen by hooking my scope up to trigger on the Lucent, setting the BG7TBL up on the other channel with infinite persistence, and then measuring the horizontal deviation of the two waveforms. Is this an indication that this version of the BG7TBL does not have the slightly off frequency issue?
I will see if I can get TimeLab up and running next.
Sorry, but you're still doing snapshots. Your StdDev measurement averages things out so that any frequency drift is completely invisible. Remember that the error was only about 2e-11 so nanoseconds are like mountains. When John Miles made his measurements, he got a phase drift of approx. 2 us per day which is about 80 ns per hour. You should be able to see that with a scope. I don't know if the GPS jitter and wobble might be enough to hide that trend unless you measure it for hours as I suggested to Lightages. You could try making a StdDev measurement for a few minutes every hour. That would help average out the short term noise. This time, the mean will be the important number. See if it's changing in a consistent manner.
Ed
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I bumped up the count on the 53131A statistics. The UI on this thing baffles me sometimes, but I think it ran for about 45 minutes or so before emitting a value.
Lucent to BG7TBL/2014-12-09 - StdDev 3.4090ns, Max 48.8ns, Min 35.3ns, (Max-Min) 13.5ns.
This value correlates well with what I've seen by hooking my scope up to trigger on the Lucent, setting the BG7TBL up on the other channel with infinite persistence, and then measuring the horizontal deviation of the two waveforms. Is this an indication that this version of the BG7TBL does not have the slightly off frequency issue?
I will see if I can get TimeLab up and running next.
Sorry, but you're still doing snapshots. Your StdDev measurement averages things out so that any frequency drift is completely invisible. Remember that the error was only about 2e-11 so nanoseconds are like mountains. When John Miles made his measurements, he got a phase drift of approx. 2 us per day which is about 80 ns per hour. You should be able to see that with a scope. I don't know if the GPS jitter and wobble might be enough to hide that trend unless you measure it for hours as I suggested to Lightages. You could try making a StdDev measurement for a few minutes every hour. That would help average out the short term noise. This time, the mean will be the important number. See if it's changing in a consistent manner.
Ed
I have Timelab up and running now. I think I may have destabilized things by diddling around with the antenna delay setting on the Lucent. It went out of locked mode and said it was adjusting the frequency for a few minutes. It's back in locked mode now, but I can see occasional spikes in the phase difference curve, so I think it's still not back to a steady state. Anyway, I will let it run for awhile and report back when I have something interesting to share.
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The BG7TBL/2014-12-09 is about to slip a whole cycle, so looks like the BG7TBL frequency bug is still there.
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I wish I had known about that bug before I purchased mine. It would have made much more sense to get the Trimble based unit, no?
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I wish I had known about that bug before I purchased mine. It would have made much more sense to get the Trimble based unit, no?
It slipped a cycle in about 6840 seconds, which equates to 9,999,999.999,854 Hz. I guess for many purposes it doesn't matter. However, IMHO there's a bigger downside to this unit which is that there's no ability to control or monitor things other than the NMEA data via the serial port.
Have you cracked it open to see what's inside? I know it's a Morion OCXO, but what is the micro? It might make a decent GPSDO if an alternate firmware could be loaded. Probably some Wun Hung Lo microcontroller, but maybe it's something decent?
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Have you cracked it open to see what's inside? I know it's a Morion OCXO, but what is the micro? It might make a decent GPSDO if an alternate firmware could be loaded. Probably some Wun Hung Lo microcontroller, but maybe it's something decent?
Its a Mega8 in mine, standard pin pad for programming too. see pic.
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Have you cracked it open to see what's inside? I know it's a Morion OCXO, but what is the micro? It might make a decent GPSDO if an alternate firmware could be loaded. Probably some Wun Hung Lo microcontroller, but maybe it's something decent?
Its a Mega8 in mine, standard pin pad for programming too. see pic.
Ok, that's good news. He must be using that Altera CPLD for glue logic, that MAX232 to drive the serial port, and I assume there's a D/A in there somewhere to drive the ECF voltage. Should be open to reverse engineering. Is it worth the effort?
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Time for a sanity check people!
Moto has confirmed that the frequency is off by 1.5e-11. That's 0.000 146 Hz on a 10 MHz signal.
A Rubidium oscillator straight from the factory is typically adjusted to within 5.0e-11. Lightages will see his FE-5680B move this much just from temperature changes. A Rubidium's monthly drift will be that much or more.
An HP/Symmetricom 5071A Cesium standard when averaged over a 1 sec. period is only stable to 1.2e-11.
It's one thing to look at two units and say that one is better because the 'bad' unit has this error. It's damned annoying to find that something that's supposed to be dead on 10 MHz isn't! It would probably cause you to choose a different unit if you're shopping for one. But it doesn't mean that the unit is trash. As I've said before, the BG7TBL unit will provide good service for the vast majority of users. If you've already got one it'd be hard to find a situation where this unit can't do the job.
If I had one of these units I'd file this info away in the back of my head and carry on. If necessary, I'd make a correction in any measurements to compensate for the error. But such a correction would be very rare. I have many other things I'd rather do than try to reverse engineer something like this to correct such a small error. Don't even consider it unless you're a PLL guru who can design digital PID controllers in your sleep!
Ed
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Oh I wasn't going to do anything to mine. Just like you said if I had known before I purchased it I would have chosen the other. I can't use better accuracy than it has even with the error.
And yes, I was playing around today and I can move the frequency of the FE5680B with cooling fan speed. They are so close in frequency that I can make it faster or slower just by blowing different amounts of air over the case of the 5680.
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Time for a sanity check people!
You are right, of course. I guess this is why they call the mailing list "time nuts". I still think it would be interesting to develop the firmware for one of these things. Maybe BG7TBL could even be persuaded to give up the source code. Of course, I need another "project" like I need a hole in the head.
BTW, is there any good reference on now these units work? Is it just counting the 10M osc cycles in a 1 PPS interval from the GPS, subtracting that from the target value (10M) to derive an error signal that drives a PID loop controlling the EFC voltage?
I bet that Altera MAX CPLD is doing that count of 10M cycles in 1 PPS intervals. I wonder how one deals with metastability issues.
Or maybe it is working more like a PLL, with a phase comparator...
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Time for a sanity check people!
You are right, of course. I guess this is why they call the mailing list "time nuts". I still think it would be interesting to develop the firmware for one of these things. Maybe BG7TBL could even be persuaded to give up the source code. Of course, I need another "project" like I need a hole in the head.
BTW, is there any good reference on now these units work? Is it just counting the 10M osc cycles in a 1 PPS interval from the GPS, subtracting that from the target value (10M) to derive an error signal that drives a PID loop controlling the EFC voltage?
I bet that Altera MAX CPLD is doing that count of 10M cycles in 1 PPS intervals. I wonder how one deals with metastability issues.
Or maybe it is working more like a PLL, with a phase comparator...
We know nothing about Mr. BG7TBL. He's obviously very talented. We don't know if he just made a mistake or if he's operating at the edge of his knowledge level. Is it significant that he's started producing units that reuse existing GPSDOs rather than his own? Or was that just because those other units are available? No way to tell.
I don't remember a specific low-level writeup on how GPSDOs work. There are lots of amateur projects around. Some use digital technology, others use analog. Google for "Brooks Shera". His was one of the first hobbyist GPSDOs that came out. Maybe it was the first. He passed away a few years ago, but his source code was saved and has been released. James Miller came up with a very well known GPSDO that's based on very simple analog technology and performs very well. I would think that any training material on FLL or PLL systems would be useful.
A few years ago I had an eerily similar situation where a commercial GPS receiver had a 10 MHz output that was about 1.5e-11 off frequency. It turned out that the firmware implemented an FLL rather than a PLL. The vendor had a PLL version in his archives that solved the problem.
Ed
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Time for a sanity check people!
You are right, of course. I guess this is why they call the mailing list "time nuts". I still think it would be interesting to develop the firmware for one of these things. Maybe BG7TBL could even be persuaded to give up the source code. Of course, I need another "project" like I need a hole in the head.
BTW, is there any good reference on now these units work? Is it just counting the 10M osc cycles in a 1 PPS interval from the GPS, subtracting that from the target value (10M) to derive an error signal that drives a PID loop controlling the EFC voltage?
I bet that Altera MAX CPLD is doing that count of 10M cycles in 1 PPS intervals. I wonder how one deals with metastability issues.
Or maybe it is working more like a PLL, with a phase comparator...
We know nothing about Mr. BG7TBL. He's obviously very talented. We don't know if he just made a mistake or if he's operating at the edge of his knowledge level. Is it significant that he's started producing units that reuse existing GPSDOs rather than his own? Or was that just because those other units are available? No way to tell.
I don't remember a specific low-level writeup on how GPSDOs work. There are lots of amateur projects around. Some use digital technology, others use analog. Google for "Brooks Shera". His was one of the first hobbyist GPSDOs that came out. Maybe it was the first. He passed away a few years ago, but his source code was saved and has been released. James Miller came up with a very well known GPSDO that's based on very simple analog technology and performs very well. I would think that any training material on FLL or PLL systems would be useful.
A few years ago I had an eerily similar situation where a commercial GPS receiver had a 10 MHz output that was about 1.5e-11 off frequency. It turned out that the firmware implemented an FLL rather than a PLL. The vendor had a PLL version in his archives that solved the problem.
Ed
One of my coworkers has emailed and received responses from BG7TBL. I'll batch up my questions and see if he can get some answers.
I found the Shera articles on my own after posting this; he has an article on his website as well as a link to a PDF of a QST article. Good articles. I see now how it is able to detect phase differences < 1 cycle. At least for Shera, he has something running at a frequency higher than 10MHz to do that. I guess you could also do it with the usual XOR or R/S flip-flop and some sort of filter to turn that into an analog voltage, and then sample that at whatever rate suits your fancy.
BTW - I have been reading up on the UBlox modules, and they actually have a module that will discipline an external frequency reference directly. It has an output you can hook to a DAC, and a frequency input, and some configuration you write to tell it what the frequency is, what the range and gain is of the frequency adjustment, what the stability of the reference is, etc. I wonder how well that works? Might make for an extremely compact GPSDO.
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i received some documentation from ocilloquartz for star4. looks like there we should have rs232 access to the controller. i'm going to verify if it's ok to redistribute.
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I was off in my calculation on the error of the BG7TBL/2014-12-09. I misinterpreted the Timelab graph as showing degrees, when in fact it was showing seconds. So it is actually slipping a cycle every 1800 seconds. This works out to an effective frequency of 9,999,999.999444
Not a huge difference, but I wanted to correct the record.
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Here are some Timelab graphs showing the Lucent KS-24361 versus the latest BG7TBL attempt as well as the two 3rd-party units he is putting his logo on.
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Hmm-I bought the BG7TBL/2014-12-09 because it was the most-recommended.
What is the now-most-recommended? I haven't even had a chance to power on the BG7TBL/2014-12-09 unit :-\
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Hmm-I bought the BG7TBL/2014-12-09 because it was the most-recommended.
What is the now-most-recommended? I haven't even had a chance to power on the BG7TBL/2014-12-09 unit :-\
Depends on your use for it. There's nothing wrong with it unless a frequency difference of 0.0006 Hz causes you problems. FOr 99.99999% of the people out there, this is a non-issue. It is a nice compact unit that works just fine.
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Hmm-I bought the BG7TBL/2014-12-09 because it was the most-recommended.
What is the now-most-recommended? I haven't even had a chance to power on the BG7TBL/2014-12-09 unit :-\
Depends on your use for it. There's nothing wrong with it unless a frequency difference of 0.0006 Hz causes you problems. FOr 99.99999% of the people out there, this is a non-issue. It is a nice compact unit that works just fine.
This is certainly a want vs need situation. My use is only in calibrating my frequency counters and rubidium oscillators, and synchronizing my other equipment. In that regard, The Lucent I have and the BG7TBL/2014-12-09 are likely perfectly fine for this use case. However, I want the "best" (a balanced combination of most accurate/stable within a reasonable price bracket).
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Hmm-I bought the BG7TBL/2014-12-09 because it was the most-recommended.
What is the now-most-recommended? I haven't even had a chance to power on the BG7TBL/2014-12-09 unit :-\
Depends on your use for it. There's nothing wrong with it unless a frequency difference of 0.0006 Hz causes you problems. FOr 99.99999% of the people out there, this is a non-issue. It is a nice compact unit that works just fine.
This is certainly a want vs need situation. My use is only in calibrating my frequency counters and rubidium oscillators, and synchronizing my other equipment. In that regard, The Lucent I have and the BG7TBL/2014-12-09 are likely perfectly fine for this use case. However, I want the "best" (a balanced combination of most accurate/stable within a reasonable price bracket).
I personally like the Huawei (Star4) unit. There is some updated info coming on that one shortly that I think will make it even more attractive.
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^^^ Speaking of that...
Usagi, have you heard back from them. I'm still waiting.
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oscilloquartz sent me some basic technical documentation, and gave the OK to release it.
this product is discontinued, this document is provided as-is with no warranty. oscilloquartz cannot provide technical support for this product, so please don't bug them 8)
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I have the 2015-07-06 / Huawei version. I've tried the serial connection through Putty at 4800/8/n/1 as well as other baud rates, but don't get anything intelligible (looks like binary data, not ASCII). What are the correct serial port settings, or should I not expect ASCII?
Datasheet for the Ublox receiver:
http://www.amtechs.co.jp/2_gps/pdf/LEA-5T.pdf (http://www.amtechs.co.jp/2_gps/pdf/LEA-5T.pdf)
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oscilloquartz sent me some basic technical documentation, and gave the OK to release it.
this product is discontinued, this document is provided as-is with no warranty. oscilloquartz cannot provide technical support for this product, so please don't bug them 8)
Thank you for working with them to get this. I can confirm that the TOD output works - 4800/8/N/2, Pin 6B on the connector just as it says in the docs. I need to switch one wire over and I can check the management interface.
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I have the 2015-07-06 / Huawei version. I've tried the serial connection through Putty at 4800/8/n/1 as well as other baud rates, but don't get anything intelligible (looks like binary data, not ASCII). What are the correct serial port settings, or should I not expect ASCII?
Datasheet for the Ublox receiver:
http://www.amtechs.co.jp/2_gps/pdf/LEA-5T.pdf (http://www.amtechs.co.jp/2_gps/pdf/LEA-5T.pdf)
radioFlash - the default wiring on that unit is to expose the serial transmit from the UBlox GPS chip on the board. You can install the u-center application from UBlox to view that (it is binary) - it's using 9600/8/N/1. However, it's a read-only interface, which u-center isn't expecting, so some things don't work right.
If you want to do a little soldering, you can swap out that wire for one of the connections to the 26-pin connector on the Oscilloquartz board inside. This will let you either receive the TOD output at 4800 baud, or (in theory - not tested yet) communicate with the board's management interface (9600/8/N/2). This connector and the two serial interfaces are discussed in the manual that usagi attached to his post a few up from this one.
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radioFlash - the default wiring on that unit is to expose the serial transmit from the UBlox GPS chip on the board. You can install the u-center application from UBlox to view that (it is binary) - it's using 9600/8/N/1. However, it's a read-only interface, which u-center isn't expecting, so some things don't work right.
If you want to do a little soldering, you can swap out that wire for one of the connections to the 26-pin connector on the Oscilloquartz board inside. This will let you either receive the TOD output at 4800 baud, or (in theory - not tested yet) communicate with the board's management interface (9600/8/N/2). This connector and the two serial interfaces are discussed in the manual that usagi attached to his post a few up from this one.
Thanks for clearing it up--I'll have a try with u-center for now.
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Management interface works too. It's very picky about end-of-line characters, which is a PITA when using Putty because it does not give you control over what it sends. You need to send "<command>;<cr><lf>".
Here's the response to the INV command:
INV=GPS STAR 4+,015880,1057,01,015881,0149,11022010,0010,8663-XS,0152;
This is:
INV=a,b,c,d,e,f,g,h,i;<cr><lf>
a: Name of the module (Max 12 char.) : GPS STAR 4+
b: Article number (Max. 6 characters) : 015880
c: Serial Number (Max: 6 characters) : 1057
d: Hardware version (Max. 2 characters): 01
e: Firmware article number (6 characters) : 015881
f: Firmware version (4 characters) : 0149
g: Date of test (format : DD/MM/YYYY) : 11/02/2010
h: Version of test system (Max. 4 characters) : 0010
i : Oscillator's type ( Max. 10 characters) : 8663-XS
j: FPGA version (4 characters) : 0152
Please post your units response to this command if you wire up the management interface. I'd like to see what range of firmware/hardware versions are out there.
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Thanks for the info usagi et al.
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Another useful command: TEMPERATURE
This is probably the temperature from the FPGAs internal sensor. Very useful to see if things are overheating inside that non-ventilated BG7TBL enclosure. Mine is out of the enclosure at the moment, but I'll run it later when it's all buttoned up and see what it says. Out of the enclosure, it's reading +40.72.
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Here are some Timelab graphs showing the Lucent KS-24361 versus the latest BG7TBL attempt as well as the two 3rd-party units he is putting his logo on.
Very interesting!
If you ran the Allen Deviation graphs longer you'd see more of the behaviour of the units. Notice how they all line up on the left side of the graph? That's the effect of your 53131A counter. It's only when they deviate from that line that you see the interaction of the GPSDOs.
The phase graph really shows the frequency error doesn't it? If you hit the 'r' key, TimeLab will take a linear best fit of each graph and then subtract it from the graph. The frequency offset will disappear and you'll see the short-term comparison of the units. This would give you an idea what would happen if you used the 10 MHz as a reference for your counter, generator, etc.
Ed
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Here are some Timelab graphs showing the Lucent KS-24361 versus the latest BG7TBL attempt as well as the two 3rd-party units he is putting his logo on.
Very interesting!
If you ran the Allen Deviation graphs longer you'd see more of the behaviour of the units.
I tried to run the Allan Deviation for longer, but for some reason Timelab just stops capturing after some time. It's not the value I set in the Acquisition settings, it stops even if I set it to only stop on Manual Termination.
Notice how they all line up on the left side of the graph? That's the effect of your 53131A counter. It's only when they deviate from that line that you see the interaction of the GPSDOs.
I suspected this. I even tried calibrating some of the other aspects of the counter like offset, gain, and the Time Interval calibration. I think the offset and gain calibrations were fine, but the time interval calibration made things worse. This counter has a "quick" mode of calibration of that which can be done without any fancy equipment, but the fine mode requires things I don't have. So by doing the quick cal, I think I actually made it worse.
The phase graph really shows the frequency error doesn't it? If you hit the 'r' key, TimeLab will take a linear best fit of each graph and then subtract it from the graph. The frequency offset will disappear and you'll see the short-term comparison of the units. This would give you an idea what would happen if you used the 10 MHz as a reference for your counter, generator, etc.
Ed
Take a gander at the updates on the Huawei/Star4+ unit above. This is looking like a really good option now that we have a management interface working.
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Reported temperature of the Huawei, in the enclosure, sitting on top of the heat-generating Lucent, is 51~52C.
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I don't remember a specific low-level writeup on how GPSDOs work.
The Trimble Thunderbolt manual has some reasonable light info on how it works and mentions Allan Variance and Kalman Filtering in section 5 of its op manual here...
ftp://ftp.trimble.com/pub/sct/embedded/bin/Manuals/ThunderBoltBook2003.pdf (http://ftp://ftp.trimble.com/pub/sct/embedded/bin/Manuals/ThunderBoltBook2003.pdf)
A much deeper discussion can be found from NIST here...
"The Use of GPS Disciplined Oscillators as Primary Frequency Standards for Calibration and Metrology Laboratories"
http://tf.nist.gov/general/pdf/2297.pdf (http://tf.nist.gov/general/pdf/2297.pdf)
regards
Tim
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Here are some Timelab graphs showing the Lucent KS-24361 versus the latest BG7TBL attempt as well as the two 3rd-party units he is putting his logo on.
Very interesting!
If you ran the Allen Deviation graphs longer you'd see more of the behaviour of the units.
I tried to run the Allan Deviation for longer, but for some reason Timelab just stops capturing after some time. It's not the value I set in the Acquisition settings, it stops even if I set it to only stop on Manual Termination.
Notice how they all line up on the left side of the graph? That's the effect of your 53131A counter. It's only when they deviate from that line that you see the interaction of the GPSDOs.
I suspected this. I even tried calibrating some of the other aspects of the counter like offset, gain, and the Time Interval calibration. I think the offset and gain calibrations were fine, but the time interval calibration made things worse. This counter has a "quick" mode of calibration of that which can be done without any fancy equipment, but the fine mode requires things I don't have. So by doing the quick cal, I think I actually made it worse.
The phase graph really shows the frequency error doesn't it? If you hit the 'r' key, TimeLab will take a linear best fit of each graph and then subtract it from the graph. The frequency offset will disappear and you'll see the short-term comparison of the units. This would give you an idea what would happen if you used the 10 MHz as a reference for your counter, generator, etc.
Ed
Take a gander at the updates on the Huawei/Star4+ unit above. This is looking like a really good option now that we have a management interface working.
I can't imagine why Timelab would just stop. I've run it for days. Does it just stop acquiring or does it pop up some kind of dialog box?
Calibration won't affect the sloped line on the left side of the Allen Deviation graphs. That's determined by the counter's resolution. Notice that at 1 second on the X-axis, the graphs are at about 7e-10. The 53131A has a resolution of 500 ps, i.e. 5e-10. That's not a coincidence. The one second Allen Deviation is slightly higher than the counter's resolution.
I saw the info on the Oscilloquartz Star 4. Very nice! But I see that there are no more units available. Hopefully some more will appear soon.
Ed
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I can't imagine why Timelab would just stop. I've run it for days. Does it just stop acquiring or does it pop up some kind of dialog box?
Calibration won't affect the sloped line on the left side of the Allen Deviation graphs. That's determined by the counter's resolution. Notice that at 1 second on the X-axis, the graphs are at about 7e-10. The 53131A has a resolution of 500 ps, i.e. 5e-10. That's not a coincidence. The one second Allen Deviation is slightly higher than the counter's resolution.
I saw the info on the Oscilloquartz Star 4. Very nice! But I see that there are no more units available. Hopefully some more will appear soon.
Ed
It just stops. I'll run another capture tonight and post the results to show you what happens.
My thinking on the calibration was that if the gain and offset setting could be causing triggering somewhere other than the ideal center crossing of the square wave, in turn leading to more jitter. Maybe not, but I figured it couldn't hurt to calibrate it.
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Ok, here are some screen grabs showing the issue. The first image shows that it's just stopped sampling at 200,000 points, even though this is far short of the 10,000 seconds I told it to capture. The second graph shows the settings that I used.
Note that it says "Acquiring (100%)" although this does not show up on the screen capture. It was set to capture 10,000 seconds but to continue until manually stopped. It says it has captured 200,000 pts, and if you divide 10,000 seconds by the Sample Interval value it's automatically selected, 0.05s, this gives 200,000. I suspect the issue likes somewhere with the sample interval it chose. Perhaps it chose a number of sample points up front, but then used a different sample interval and so ended up finishing early. Still, it was told to continue until manually stopped, so it shouldn't have stopped...
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I see what the issue is. It IS capturing for 10,000 seconds, but that doesn't equate to an Allan Deviation graph with information at 10,000 seconds. If you go to the phase plot, you can see that it does run to 10,000 seconds.
I'm not sure why the setting to run until manually stopped isn't working, but I'll just crank up the Trace Duration value and let it run longer.
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I see what the issue is. It IS capturing for 10,000 seconds, but that doesn't equate to an Allan Deviation graph with information at 10,000 seconds. If you go to the phase plot, you can see that it does run to 10,000 seconds.
I'm not sure why the setting to run until manually stopped isn't working, but I'll just crank up the Trace Duration value and let it run longer.
You might want to ask John Miles about this. It doesn't sound like it's doing what he intended. If you hover your mouse over the 'Run Until' field you'll see some help text. It sounds like it's supposed to be a moving window with the length that's set in 'Trace Duration'. I've never used that setting.
By the way, if you want to find the noise floor of your counter, take any signal (i.e. the Lucent's 10 or 15 MHz), split it, either with an actual splitter or just a BNC 'T' adapter, and feed it through two different length cables to the A and B inputs. Then measure the time delay between the inputs. This is a best case measurement. Graph the results and you'll see how your counter is performing. Make sure that the cables can't move around or fall off the table. That will affect the results.
Ed
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Has somebody found monitor program for this trimble disciplined version BG7TBL 2015-07-17? Does Tboltmon work?
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By the way, if you want to find the noise floor of your counter, take any signal (i.e. the Lucent's 10 or 15 MHz), split it, either with an actual splitter or just a BNC 'T' adapter, and feed it through two different length cables to the A and B inputs. Then measure the time delay between the inputs. This is a best case measurement. Graph the results and you'll see how your counter is performing. Make sure that the cables can't move around or fall off the table. That will affect the results.
Ed
Nice tip ed :-+
I'll have to give it a try with my PM6680B , and maybe the 5370B
/Bingo
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By the way, if you want to find the noise floor of your counter, take any signal (i.e. the Lucent's 10 or 15 MHz), split it, either with an actual splitter or just a BNC 'T' adapter, and feed it through two different length cables to the A and B inputs. Then measure the time delay between the inputs. This is a best case measurement. Graph the results and you'll see how your counter is performing. Make sure that the cables can't move around or fall off the table. That will affect the results.
Ed
Nice tip ed :-+
I'll have to give it a try with my PM6680B , and maybe the 5370B
/Bingo
That idea isn't mine. It came from Magnus.......or Tom.......or John........or Didier.....hell, I don't remember. It was one of those nutty guys. :)
Ed
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You might want to ask John Miles about this. It doesn't sound like it's doing what he intended. If you hover your mouse over the 'Run Until' field you'll see some help text. It sounds like it's supposed to be a moving window with the length that's set in 'Trace Duration'. I've never used that setting.
I did read all that help text already. In any event, just setting the duration to 100,000s seems to have solved the immediate problem. It's currently got about 4000s of Allan Deviation captured, and it says "Acquiring (26%)" so it seems like we should at least get 10,000s outof it.
Also note - now that I have the Huawei/Star4+ management interface working, I can see that it's not yet switched itself into its holdover stability mode, so I expect performance here will get better as the crystal ages in and it switches into that mode and increases the time constant on the adjustment loop. These units are really nice, definitely my favorite now.
By the way, if you want to find the noise floor of your counter, take any signal (i.e. the Lucent's 10 or 15 MHz), split it, either with an actual splitter or just a BNC 'T' adapter, and feed it through two different length cables to the A and B inputs. Then measure the time delay between the inputs. This is a best case measurement. Graph the results and you'll see how your counter is performing. Make sure that the cables can't move around or fall off the table. That will affect the results.
Ok, I will give that a try. I did try connecting the same signal via two equal length cables, and I can see that 500ps resolution pretty clearly. FOr that matter, I can see it when comparing two of the GPSDO. The short term readings all seen to jitter by that 500ps value (at least as near as I can tell trying to read a display that is updating tens of times a second).
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I see what the issue is. It IS capturing for 10,000 seconds, but that doesn't equate to an Allan Deviation graph with information at 10,000 seconds. If you go to the phase plot, you can see that it does run to 10,000 seconds.
I'm not sure why the setting to run until manually stopped isn't working, but I'll just crank up the Trace Duration value and let it run longer.
You might want to ask John Miles about this. It doesn't sound like it's doing what he intended. If you hover your mouse over the 'Run Until' field you'll see some help text. It sounds like it's supposed to be a moving window with the length that's set in 'Trace Duration'. I've never used that setting.
By the way, if you want to find the noise floor of your counter, take any signal (i.e. the Lucent's 10 or 15 MHz), split it, either with an actual splitter or just a BNC 'T' adapter, and feed it through two different length cables to the A and B inputs. Then measure the time delay between the inputs. This is a best case measurement. Graph the results and you'll see how your counter is performing. Make sure that the cables can't move around or fall off the table. That will affect the results.
Ed
It ws just my misunderstanding of how the ADEV calculation works.
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Has somebody found moitor program for this trimble disciplined version BG7TBL 2015-07-17? Does Tboltmon work?
No it does not. The only software that I know which works is opening a terminal session and typing in the command.
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Ed - as requested - here is a longer Timelab capture for the Huawei. It stopped a bit earlier than I wanted, but I couldn't figure out how to extend the capture.
Reading the specs on this unit, I think my measurement set-up is not sufficient to really show what this GPSDO is capable of. It would be great if someone with something better than a 53131A counter could capture some data on this.
-
I can see that it's not yet switched itself into its holdover stability mod
Hi
Holdover and position hold are two different things. Holdover is when a GPSDO loses GPS and tries to maintain performance without it. Position hold is when the initial survey completes and the GPSDO switches into timing mode.
How long is the default initial survey on these units? Is there a way to run a longer precision survey? (Especially in the one with the LEA-5T)
How good is the PPS signal on these things? One measurement you can try is the TI between a reference PPS and the PPS edge of the DUT. This will tell you how well it maintains alignment of the PPS throughout the day. You will likely need to offset the reference so that the measured value doesn't drift across zero or cause the 53131A to re-scale the units. You are still limited by the 500ps resolution, but drift will likely be +/- tens of ns, so there is still meaningful data to be seen.
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Management interface works too. It's very picky about end-of-line characters, which is a PITA when using Putty because it does not give you control over what it sends. You need to send "<command>;<cr><lf>".
Here's the response to the INV commands. The hardware and firmware versions are the same as yours.
INV=GPS STAR 4+,015880,1057,01,015881,0149,11022010,0010,8663-XS,0152;
This is:
INV=a,b,c,d,e,f,g,h,i;<cr><lf>
a: Name of the module (Max 12 char.) : GPS STAR 4+
b: Article number (Max. 6 characters) : 015880
c: Serial Number (Max: 6 characters) : 1057
d: Hardware version (Max. 2 characters): 01
e: Firmware article number (6 characters) : 015881
f: Firmware version (4 characters) : 0149
g: Date of test (format : DD/MM/YYYY) : 11/02/2010
h: Version of test system (Max. 4 characters) : 0010
i : Oscillator's type ( Max. 10 characters) : 8663-XS
j: FPGA version (4 characters) : 0152
Please post your units response to this command if you wire up the management interface. I'd like to see what range of firmware/hardware versions are out there.
Here are responses to some of the various management commands:
INV;
INV=GPS STAR 4+,015880,1508,01,015881,0149,14042010,0010,8663-XS,0152;
CONF;
CONF=200,200,A,+00:00,+0;
ALARM;
ALARM=9;
GPS_TIME;
GPS_TIME=1859,437242,30.06.15,23:59:59,00,17;
INFO_TRACK_SAT;
INFO_TRACK_SAT=8,
1,14,
2,18,
3,21,
4,22,
5,24,
6,29,
7,135,
8,138;
STATUS;
STATUS=3,O,T;
TEMPERATURE;
TEMPERATURE=+40.41;
TYPE;
TYPE=4554,BASE;
ATDC_STATUS;
ATDC_STATUS=1,990;
HOLD_PERF_STATUS;
HOLD_PERF_STATUS=0;
INFO_VIS_SAT;
INFO_VIS_SAT=16,
1,138,54,197,43,2,
2,18,55,308,43,2,
3,135,39,234,42,2,
4,29,36,181,45,2,
5,122,32,242,0,1,
6,22,25,274,38,2,
7,20,37,51,0,2,
8,21,69,352,17,2,
9,24,24,124,29,2,
10,13,16,39,0,2,
11,26,1,257,0,2,
12,14,15,209,41,2,
13,15,48,48,17,2,
14,27,10,320,0,2,
15,16,2,283,0,2,
16,10,165,0,0,1;
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Ed - as requested - here is a longer Timelab capture for the Huawei. It stopped a bit earlier than I wanted, but I couldn't figure out how to extend the capture.
Reading the specs on this unit, I think my measurement set-up is not sufficient to really show what this GPSDO is capable of. It would be great if someone with something better than a 53131A counter could capture some data on this.
Yes, I think you're right. In your earlier graphs you could see that the BG7TBL unit was flattening out in the low e-12 range while it wasn't clear where the Lucent and Oscilloquartz units were going. Now we know that your counter's performance has merged with what I call the 'GPS line'. It's the approximate performance limit of any GPSDO. Early in the 'economical frequency standard' thread I think I had it on one of my graphs.
Let me see now, so far you've got a counter that's good enough for all normal uses and *three* GPSDOs and now you're complaining that your counter isn't good enough. Moto, you're a Time-Nut! ;D
Ed
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INV=GPS STAR 4+,015880,1057,01,015881,0149,11022010,0010,8663-XS,0152;
This is:
INV=a,b,c,d,e,f,g,h,i;<cr><lf>
a: Name of the module (Max 12 char.) : GPS STAR 4+
b: Article number (Max. 6 characters) : 015880
c: Serial Number (Max: 6 characters) : 1057
d: Hardware version (Max. 2 characters): 01
e: Firmware article number (6 characters) : 015881
f: Firmware version (4 characters) : 0149
g: Date of test (format : DD/MM/YYYY) : 11/02/2010
h: Version of test system (Max. 4 characters) : 0010
i : Oscillator's type ( Max. 10 characters) : 8663-XS
j: FPGA version (4 characters) : 0152
Please post your units response to this command if you wire up the management interface. I'd like to see what range of firmware/hardware versions are out there.
INV;
INV=GPS STAR 4+,015880,1508,01,015881,0149,14042010,0010,8663-XS,0152;
Thanks. Looks like same firmware, hardware, and FPGA versions.
BTW - the Alarm 9 should go away after some time. My units is finally showing no alarms, holdover performance status = match specification, and atdc status = activated. It took about 2 days after my powering it back up to reach that state.
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Ed - as requested - here is a longer Timelab capture for the Huawei. It stopped a bit earlier than I wanted, but I couldn't figure out how to extend the capture.
Reading the specs on this unit, I think my measurement set-up is not sufficient to really show what this GPSDO is capable of. It would be great if someone with something better than a 53131A counter could capture some data on this.
Yes, I think you're right. In your earlier graphs you could see that the BG7TBL unit was flattening out in the low e-12 range while it wasn't clear where the Lucent and Oscilloquartz units were going. Now we know that your counter's performance has merged with what I call the 'GPS line'. It's the approximate performance limit of any GPSDO. Early in the 'economical frequency standard' thread I think I had it on one of my graphs.
Let me see now, so far you've got a counter that's good enough for all normal uses and *three* GPSDOs and now you're complaining that your counter isn't good enough. Moto, you're a Time-Nut! ;D
Ed
I am some kind of nut, that's for sure.
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I was asked on the other thread for details on the RS232 mod to the Huawei/Star4+ module. It is really trivial if you will just read the manual that usagi linked, but I did put some notes and a few pictures up for the poster in the other thread. Here is a link to that in case it is helpful to anyone here:
https://www.eevblog.com/forum/testgear/economical-option-for-precision-frequency-reference/255/ (https://www.eevblog.com/forum/testgear/economical-option-for-precision-frequency-reference/255/)
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Hi guys/gals,
since the Huawei/Star4+ board (with LEA-5T GPS chip) is not available anymore from eBay sellers, I looked into alternatives. I know, the frequency stability between different bg7tbl variants is unsignificant for normal uses and thus any board should do. However I won't be able to set outdoor antenna and that's why I was interested mainly on the Huawei-variant.
Now, LEA-5T is discontinued but there's a new chip, LEA-6T available.
There are two vendors selling evaluation boards:
http://shop.sysmocom.de/products/osmo-lea6t-gps (http://shop.sysmocom.de/products/osmo-lea6t-gps)
and
http://www.csgshop.com/product.php?id_product=127 (http://www.csgshop.com/product.php?id_product=127)
For 181 EUR and 147 USD, they are bit expensive. Osmocom one seems more documented (it has even it's full schematics and board layout available as Git repository!). They also have USB connectivity. However they do lack OCXO.
What do you think, how hard would it be to bypass the GPS chip on these other bg7tbl variants and hook the ref board output there instead?
Alternatively one could start making these add-on boards too. The chips are quite expensive if bought separately (134 euros(!) in their web shop), but in quantities > 10 less than 50 eur/chip.
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without ocxo i don't think they will generate much interest for those looking for a precision frequency reference. especially not at that price while surplus gpsdo with ocxo are still widely available.
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What GPSDO would you recommend for indoor use? I remember someone complaining about the reception of Trimble variant earlier, but otherwise that would have been my 2nd choice.
BTW. How does the Jupiter chip in James Miller's GPSDO
(http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm (http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm)) compare to Trimble and Huawei boards in this regard?
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What GPSDO would you recommend for indoor use? I remember someone complaining about the reception of Trimble variant earlier, but otherwise that would have been my 2nd choice.
BTW. How does the Jupiter chip in James Miller's GPSDO
(http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm (http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm)) compare to Trimble and Huawei boards in this regard?
I think the BG7TBL 2014-12-09. It has a u-blox chip with good sensitivity, and should work fine if you just want a reference and don't care about software to monitor its status or the small frequency error.
That said, the operation indoors may be a bit iffy, and it will definitely hurt the accuracy of the time signal (but accuracy will still be fine if you just want a frequency reference). I just hooked up a u-blox 7th gen chip as part of a project I am doing. It is syncing 4-5 satellites sitting in a window, but was struggling a few feet back from the window. So just be aware that indoor operation may or may not work.
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You need to be more specific than just saying 'indoors'. If you're on the top floor of a wood-framed building with ordinary shingles, you'll probably be fine. If you've got six stories above you or a steel roof, you'll have to find a window that preferably faces towards the equator.
The Jupiter boards, like all older boards, are a bit deaf by modern standards. If you've got a good antenna in a good location an older board will do fine. If your antenna system is less than optimum, an older board could have problems or you might have to add an in-line amplifier.
Ed
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Ed and Motocoder, thanks for your advice.
I'm living in a 4 story building (my apartment in 3rd story). It's an old apartment made mostly of bricks, so not so much steel&concrete here I think, except for the roof which is in fact steel.. :palm: I might be able to setup the antenna outside facing the western window, but even then there's another building blocking the horizon, so there would be a cone of unobstructed sky approximately 45 deg vertically and 170 deg sideways.
My main use case would be to check the calibration of high stability OCXOs in my equipment, but in the future the go-to frequency standard at my lab would be rubidium anyway (that would be then checked every 1-2 months with GPSDO).
As suggested by motocoder, I think I'll settle for the 2014-12-09 variant then, as it seems to be the most sensitive of the GPSDOs available currently (unless the guy from 168electronics comes to his senses and starts selling his stock of Star4+ boards (190 left!) :wtf: ).
Most eBay vendors send items with the hockey puck (patch?) type antenna, but I think the cone / half-sphere shaped (helical?) antenna is recommended for time measurements. Have you in practice seen much difference in reception with these?
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Ed and Motocoder, thanks for your advice.
I'm living in a 4 story building (my apartment in 3rd story). It's an old apartment made mostly of bricks, so not so much steel&concrete here I think, except for the roof which is in fact steel.. :palm: I might be able to setup the antenna outside facing the western window, but even then there's another building blocking the horizon, so there would be a cone of unobstructed sky approximately 45 deg vertically and 170 deg sideways.
My main use case would be to check the calibration of high stability OCXOs in my equipment, but in the future the go-to frequency standard at my lab would be rubidium anyway (that would be then checked every 1-2 months with GPSDO).
As suggested by motocoder, I think I'll settle for the 2014-12-09 variant then, as it seems to be the most sensitive of the GPSDOs available currently (unless the guy from 168electronics comes to his senses and starts selling his stock of Star4+ boards (190 left!) :wtf: ).
Most eBay vendors send items with the hockey puck (patch?) type antenna, but I think the cone / half-sphere shaped (helical?) antenna is recommended for time measurements. Have you in practice seen much difference in reception with these?
I don't think the antenna is going to make a difference indoors. I'd start with the antenna that comes with the unit and save your money unless that's not working out.
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If the window sees sky ( no matter how little, the view you have will give you at least 2 signals and the GPS will eventually lock with that) just a plain GPS antenna on the sill will work. I have a small GPS that works fine just on the sill in a similar situation, and it will lock from cold in under 20 minutes. That one has a plain ceramic patch antenna, and was originally a bluetooth unit, though it does do serial comms on the charge USB mini cable ( naughty, should be USB but is serial TTL) so I hacked up a USB cable to put an old Nokia serial adaptor ( old nokia clone cable for older phones without USB) in line.
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One thing to consider is that a new, super-sensitive GPS receiver is quite capable of picking up signals that an older, slightly deaf unit would ignore. Sounds good, but you might find that the older unit performs better because it's ignoring the reflected multipath signals that you really don't want to pick up.
As I understand it, when a GPS signal gets reflected, it changes from Right Hand Circularly Polarized to Left Hand Circularly Polarized. The receiver tends to reject the left hand signal, but the rejection isn't perfect. Timing antennas usually have better filtering, both for off-frequency and wrong-polarization signals so they can perform better in less than perfect situations than a regular antenna.
Ed
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@neopticus If you are serious about wanting a reference to set others by then you need a GPSDO that's on all the time. You mention using a rubidium to run by and calibrate that by GPSDO every month or so. If that's the case then you need a very good GPSDO and it would have to be on all the time to reach a resolution that would exceed that of the rubidium.
Proper timing GPSDO's such as Trimble Thunderbolts, allow you to tune their behavior to your location. i.e. you can set an elevation mask to minimize multi-path interference, change the loop time constant and damping factors. You also need a clear view of the sky for as many satellites as possible to get the best possible accuracy.
A good GPSDO will also profile their own OCXO's so that when sats are obscured and they go into holdover, the oscillator is steered in the best possible way to maintain the highest possible accuracy until enough sats are visible again to steer things properly.
And if precise time is your thing it a good GPSDO allows you to insert a propagation delay for the length of cable between the unit and the antenna to get that last 60 odd ns out of the way.
Also it can take a month for a GPSDO to attain 1E-12 or better accuracy and keep it.
You have to ask yourself... "What level of accuracy for 10MHz or 1PPS do I want ?"
There are many proper GPSDO's for reference & timing available on eBay for such purposes without spending too much money.
e.g.
http://www.ebay.com/itm/HP-SYMMETRICOM-Z3805A-GPS-Disciplined-Oscillator-GPS-Frequency-Time-Receiver-/171293077196 (http://www.ebay.com/itm/HP-SYMMETRICOM-Z3805A-GPS-Disciplined-Oscillator-GPS-Frequency-Time-Receiver-/171293077196)
http://www.ebay.com/itm/HP-Z3815A-GPS-Frequency-Time-Receiver-GPS-disciplined-oscillator-10-Mhz-1PPS/171293069062 (http://www.ebay.com/itm/HP-Z3815A-GPS-Frequency-Time-Receiver-GPS-disciplined-oscillator-10-Mhz-1PPS/171293069062)
http://www.ebay.com/itm/FEI-PicoSync-GPS-Time-Frequency-Engine-GPS-Disciplined-Oscillator-10MHZ-PP2S/181389532308 (http://www.ebay.com/itm/FEI-PicoSync-GPS-Time-Frequency-Engine-GPS-Disciplined-Oscillator-10MHZ-PP2S/181389532308)
http://www.ebay.com/itm/HP-Z3816A-GPS-Frequency-Time-Receiver-10-Mhz-1PPS-/271906200825 (http://www.ebay.com/itm/HP-Z3816A-GPS-Frequency-Time-Receiver-10-Mhz-1PPS-/271906200825)
just to name a few.
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Sorry if this one has already been discussed, but any feedback on this? Just a monitor - any practical benefit, or just as easy/better to use a computer?
http://www.ebay.com/itm/Trimble-ThunderBoltTiming-GPS-Receiver-GPSDO-10MHz-GPS-Disciplined-Clock-Monitor-/181792660863?hash=item2a53afdd7f (http://www.ebay.com/itm/Trimble-ThunderBoltTiming-GPS-Receiver-GPSDO-10MHz-GPS-Disciplined-Clock-Monitor-/181792660863?hash=item2a53afdd7f)
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Sorry if this one has already been discussed, but any feedback on this? Just a monitor - any practical benefit, or just as easy/better to use a computer?
http://www.ebay.com/itm/Trimble-ThunderBoltTiming-GPS-Receiver-GPSDO-10MHz-GPS-Disciplined-Clock-Monitor-/181792660863?hash=item2a53afdd7f (http://www.ebay.com/itm/Trimble-ThunderBoltTiming-GPS-Receiver-GPSDO-10MHz-GPS-Disciplined-Clock-Monitor-/181792660863?hash=item2a53afdd7f)
I have something similar. There's been a few different types getting about.
These are useful if you have built your TB into a nice box and you just want to keep an eye on it. Most GPSDO's have no display since once set and tuned you only need a warning LED or two to let you know if something goes awry.
At least these displays give you an idea if something is a bit off and needs ore attention.
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@neopticus If you are serious about wanting a reference to set others by then you need a GPSDO that's on all the time. You mention using a rubidium to run by and calibrate that by GPSDO every month or so. If that's the case then you need a very good GPSDO and it would have to be on all the time to reach a resolution that would exceed that of the rubidium.
Proper timing GPSDO's such as Trimble Thunderbolts, allow you to tune their behavior to your location. i.e. you can set an elevation mask to minimize multi-path interference, change the loop time constant and damping factors. You also need a clear view of the sky for as many satellites as possible to get the best possible accuracy.
A good GPSDO will also profile their own OCXO's so that when sats are obscured and they go into holdover, the oscillator is steered in the best possible way to maintain the highest possible accuracy until enough sats are visible again to steer things properly.
And if precise time is your thing it a good GPSDO allows you to insert a propagation delay for the length of cable between the unit and the antenna to get that last 60 odd ns out of the way.
Also it can take a month for a GPSDO to attain 1E-12 or better accuracy and keep it.
You have to ask yourself... "What level of accuracy for 10MHz or 1PPS do I want ?"
There are many proper GPSDO's for reference & timing available on eBay for such purposes without spending too much money.
e.g.
http://www.ebay.com/itm/HP-SYMMETRICOM-Z3805A-GPS-Disciplined-Oscillator-GPS-Frequency-Time-Receiver-/171293077196 (http://www.ebay.com/itm/HP-SYMMETRICOM-Z3805A-GPS-Disciplined-Oscillator-GPS-Frequency-Time-Receiver-/171293077196)
http://www.ebay.com/itm/HP-Z3815A-GPS-Frequency-Time-Receiver-GPS-disciplined-oscillator-10-Mhz-1PPS/171293069062 (http://www.ebay.com/itm/HP-Z3815A-GPS-Frequency-Time-Receiver-GPS-disciplined-oscillator-10-Mhz-1PPS/171293069062)
http://www.ebay.com/itm/FEI-PicoSync-GPS-Time-Frequency-Engine-GPS-Disciplined-Oscillator-10MHZ-PP2S/181389532308 (http://www.ebay.com/itm/FEI-PicoSync-GPS-Time-Frequency-Engine-GPS-Disciplined-Oscillator-10MHZ-PP2S/181389532308)
http://www.ebay.com/itm/HP-Z3816A-GPS-Frequency-Time-Receiver-10-Mhz-1PPS-/271906200825 (http://www.ebay.com/itm/HP-Z3816A-GPS-Frequency-Time-Receiver-10-Mhz-1PPS-/271906200825)
just to name a few.
TSL, thanks for your advice. I was aware that the professional systems for timekeeping are more accurate, but since they are too insensitive (to be be used in my apartment), they were ruled out pretty fast. As such, the list of eBay items you gave is not is not useful in my case. But I appreciate the effort, and I think many budget restricted (but not open sky restricted :) ) members here will appreciate it too!
I should have been more precise (no pun intended) in my description of the use case: I mentioned checking the rubidium (as in "is it on the same ballpark as GPSDO?" or "not-drifted or completely failed") but not necessarily calibrating it to its highest possible accuracy.
As I've understood, Rb standards are accurate in 10e-11 level, and to calibrate them an accuracy of at least 10e-12 is needed, which would then require 24h running, high end GPSDO with at least few weeks uptime, as you mentioned.
Now, to my use case: Here are some examples of the OCXOs I have in my possession:
HP 53132A option 010: Temp stability: <2 x 10e-9. Turn-on stability 30 min: <5 x 10-9. Aging: <1.5 x 10e-8/month
CMU200 option B12: Temp stability < 5 × 10e–9. Turn-on stability 2h: ±5 × 10e–9. Aging ±3.5 × 10e–8/year.
HP 8657A option 001: Temp stability: <7 x 10e-9. Aging < 3 x 10e-8/month.
Calibrating these would need accuracy of just 10e-10, so anything better than this is basically just money thrown away, right?
I read the review of BG7TBL 2014-12-09 by Tim Tuck (link on the first page) and there he states: "After a few hours the frequency settles further to within a Milli Hz or so of 10MHz."
This would be accuracy of level 10e-10 to e-11 and well enough for my needs, or is there something I have failed to grasp here?
-
even the 'flawed' bg7tbl is beyond most hobbyists requirements.
-
TSL, thanks for your advice. I was aware that the professional systems for timekeeping are more accurate, but since they are too insensitive (to be be used in my apartment), they were ruled out pretty fast. As such, the list of eBay items you gave is not is not useful in my case. But I appreciate the effort, and I think many budget restricted (but not open sky restricted :) ) members here will appreciate it too!
Fair enough - or... you could add a big arsed powered antenna to them, like this guy...
http://www.ebay.com/itm/Symmetricom-58532A-GPS-L1-Reference-Antenna-NEW-IN-BOX-QTY-in-Stock-/271918319682 (http://www.ebay.com/itm/Symmetricom-58532A-GPS-L1-Reference-Antenna-NEW-IN-BOX-QTY-in-Stock-/271918319682)
This has a whopping 38dBi of gain and inbuilt filters to help overcome deafness and long cable runs. I have one of those on my roof :)
I should have been more precise (no pun intended) in my description of the use case: I mentioned checking the rubidium (as in "is it on the same ballpark as GPSDO?" or "not-drifted or completely failed") but not necessarily calibrating it to its highest possible accuracy.
As I've understood, Rb standards are accurate in 10e-11 level, and to calibrate them an accuracy of at least 10e-12 is needed, which would then require 24h running, high end GPSDO with at least few weeks uptime, as you mentioned.
Now, to my use case: Here are some examples of the OCXOs I have in my possession:
HP 53132A option 010: Temp stability: <2 x 10e-9. Turn-on stability 30 min: <5 x 10-9. Aging: <1.5 x 10e-8/month
CMU200 option B12: Temp stability < 5 × 10e–9. Turn-on stability 2h: ±5 × 10e–9. Aging ±3.5 × 10e–8/year.
HP 8657A option 001: Temp stability: <7 x 10e-9. Aging < 3 x 10e-8/month.
Calibrating these would need accuracy of just 10e-10, so anything better than this is basically just money thrown away, right?
I wouldn't consider it "throwing money away" but if you can get the resolution you want for the right $, if that spec is better than you need - that's a good thing.
I read the review of BG7TBL 2014-12-09 by Tim Tuck (link on the first page) and there he states: "After a few hours the frequency settles further to within a Milli Hz or so of 10MHz."
I did say that didn't I :)
I should do some Allen Deviation tests on this unit to see if my measurements are close or same to KE5FX's
This would be accuracy of level 10e-10 to e-11 and well enough for my needs, or is there something I have failed to grasp here?
Nope, you've grasped it :)
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Fair enough - or... you could add a big arsed powered antenna to them, like this guy...
http://www.ebay.com/itm/Symmetricom-58532A-GPS-L1-Reference-Antenna-NEW-IN-BOX-QTY-in-Stock-/271918319682 (http://www.ebay.com/itm/Symmetricom-58532A-GPS-L1-Reference-Antenna-NEW-IN-BOX-QTY-in-Stock-/271918319682)
This has a whopping 38dBi of gain and inbuilt filters to help overcome deafness and long cable runs. I have one of those on my roof :)
Nope, you've grasped it :)
I just had to "downgrade" my 40dB Lucent "IceCone" to a 26dB model.
The reason was "too strong signal", on two of my gpsdo's.
I'm using 25m quad shielded cable to a 4-chan active GPS antenna splitter (w. 10dB gain)
And that combi, delivered too much gain.
So i'd watch out for getting a 40dB with short cable runs.
/Bingo
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couldn't you just add an inline attenuator if it was too hot for a specific device?
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couldn't you just add an inline attenuator if it was too hot for a specific device?
Yep he could have done that - there are plenty of 2GHz rated units around, problem is most of them cost more than a new antenna! even if you find the cheap ones, 2 of them could end costing more than a new antenna.
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couldn't you just add an inline attenuator if it was too hot for a specific device?
Yep he could have done that - there are plenty of 2GHz rated units around, problem is most of them cost more than a new antenna! even if you find the cheap ones, 2 of them could end costing more than a new antenna.
And i'd need one with DC pass through, as the antenna still want's it's 5v.
MiniCircout have some , but i almost same price as the new 26dB
Another is the antenna-psu load sense on the GPs'es , you'd still want to load it with 50ohm , or you might end up in an antenna error from the GPS.
/Bingo
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For BG7TBL 2015-07-17 there is monitor program.
In the manual is more pictures and software You can get if if You bought this.
http://www.ebay.com/itm/181810679481?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.com/itm/181810679481?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
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I haven't keep up with this thread and the others on GPSDOs but I saw this:
http://www.ebay.com/itm/Trimble-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-Antenna-power-/131564496688?hash=item1ea1dae730 (http://www.ebay.com/itm/Trimble-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-Antenna-power-/131564496688?hash=item1ea1dae730)
It looks similar to the one in the post above by janekivi (maybe just a different seller).
Any chance these parts are really from Trimble or they just say Trimble?
Thanks
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The board inside really is made by Trimble. I have just the board itself and have been testing it out - only received it yesterday so it hasn't settled down yet. motocoder has a Trimble unit and has made some comments about it in this thread - https://www.eevblog.com/forum/testgear/economical-option-for-precision-frequency-reference/ (https://www.eevblog.com/forum/testgear/economical-option-for-precision-frequency-reference/)
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the trimble isn't a bad choice, the ublox just has far superior sensitivity.
any of the bg7tbl units are superior to the lucent imo.
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Hello !
Could someone read the configuration of the U-blox NEO-6 GPS-Receiver ?
The can be easily read with the program u-Center!
I do not know if my still fits ..!?
Many thanks ! Dieter
(http://)
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I have been trying to reconfigure mine too so I can use it for an NTP server, but the settings don't work. I am looking for help with u-blox software too.
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The ublox software is really easy to use(at least over usb) but unless there is a a memory chip for the gps receiver, any modifications to what you want differently will be interesting. You will have to dive into the U-blox documents if you want to program the chip(without powering it down). In other words you will need to trick the PC.GPS to communicate w/each other w/o sending power to each other.
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I am trying to change the baud rate and sentence types sent by the receiver, but nothing changes or sticks.
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I am trying to change the baud rate and sentence types sent by the receiver, but nothing changes or sticks.
I'm confused by all the different versions that BG7TBL has put out. Are you sure that the u-blox chip is wired to the RS-232 port? I remember that at least one version only had the transmit lead wired out so you could receive the output from the GPS chip, but you couldn't talk to it.
Ed
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"2015-09-17"
custom board with surplus russian morion mv201 (http://"http://www.morion-us.com/catalog_pdf/MV201.pdf") OCXO. gps is u-blox NEO-6M-0-001 (http://"https://www.u-blox.com/en/product/neo-6-series")
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Does anyone know what voltage the lithium battery is supposed to have? 3.6V?
I measure 1.9 volts !!
if you have the battery replaced then the settings GPS neo-6M away?
Greeting, Dieter
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Does anyone know what voltage the lithium battery is supposed to have? 3.6V?
I measure 1.9 volts !!
if you have the battery replaced then the settings GPS neo-6M away?
Greeting, Dieter
according to the datasheet, the battery is for supporting gps hotstart / warmstart. supported voltage is 1.4v - 3.6v
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-->> according to the datasheet, the battery is for supporting gps hotstart / warmstart. supported voltage is 1.4v - 3.6v
Thank you for your reply !!!!
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My BG7TBL 2015-09-17 seems to be a bit different...
- The OCXO is a Morion MV89A
- The PCB date code is older (2015-06-25)
My battery measures 2.48V
Does anyone know if this version has the same "frequency offset" as some of the earlier versions?
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I need to replace diode D11 on a Trimble 57963-C board and am not able to determine the specs. The markings don't lead to any relevant part on Google. Does anyone have any info on this diode?
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Wow. Lots of info! Anyone know what the best model to get for use in a basement? It sounds like the Oscilloquarz would have been the way to go, but these do not seem to be available anymore.
Thanks.
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I am trying to change the baud rate and sentence types sent by the receiver, but nothing changes or sticks.
Probably because the CPU driving the GPSDO is configuring the u-blox on start-up.
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Wow. Lots of info! Anyone know what the best model to get for use in a basement? It sounds like the Oscilloquarz would have been the way to go, but these do not seem to be available anymore.
Thanks.
only about 10-15 of the star4 models were on the 'bay'. I saw them when they came out, but missed out. Even tried to buy a bare board from the 168 electronics guy, and was turned down. Didn't even appear on taobao.
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I can't seem to find the command to set the Trimble 57964-80 in the BG7TBL GPSDO to use UTC Time as its output instead of GPS Time. Does anyone have that handy? Any help would be most appreciated!
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Wow. Lots of info! Anyone know what the best model to get for use in a basement? It sounds like the Oscilloquarz would have been the way to go, but these do not seem to be available anymore.
Thanks.
none of them are likely to run from the basement. you'll need to run an antenna outside. so it won't really matter which one you get.
bg7tbl has a newer revision of the morion/ublox, which may fix the counter bug. but realistlcally speaking even with the "buggy" one the error is so small as to be largely irrelevant for hobbyist needs.
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Wow. Lots of info! Anyone know what the best model to get for use in a basement? It sounds like the Oscilloquarz would have been the way to go, but these do not seem to be available anymore.
Thanks.
none of them are likely to run from the basement. you'll need to run an antenna outside. so it won't really matter which one you get.
bg7tbl has a newer revision of the morion/ublox, which may fix the counter bug. but realistlcally speaking even with the "buggy" one the error is so small as to be largely irrelevant for hobbyist needs.
Agree with this. I would also get the unit with the u-blox gps chip.
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Wow. Lots of info! Anyone know what the best model to get for use in a basement? It sounds like the Oscilloquarz would have been the way to go, but these do not seem to be available anymore.
Thanks.
none of them are likely to run from the basement. you'll need to run an antenna outside. so it won't really matter which one you get.
bg7tbl has a newer revision of the morion/ublox, which may fix the counter bug. but realistlcally speaking even with the "buggy" one the error is so small as to be largely irrelevant for hobbyist needs.
Agree with this. I would also get the unit with the u-blox gps chip.
Which one is the one with the ublox gps chip? (What markings on the unit?) Sorry, I am having trouble locating it.
Thanks.
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I assume you mean the BG7TBL 2015-09-17 .
Anyone have a line on one of those? I do not see any on ePay.
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Wow. Lots of info! Anyone know what the best model to get for use in a basement? It sounds like the Oscilloquarz would have been the way to go, but these do not seem to be available anymore.
Thanks.
none of them are likely to run from the basement. you'll need to run an antenna outside. so it won't really matter which one you get.
bg7tbl has a newer revision of the morion/ublox, which may fix the counter bug. but realistlcally speaking even with the "buggy" one the error is so small as to be largely irrelevant for hobbyist needs.
Agree with this. I would also get the unit with the u-blox gps chip.
Which one is the one with the ublox gps chip? (What markings on the unit?) Sorry, I am having trouble locating it.
Thanks.
all bg7tbl models except the "2015-07-17" version have the ublox gps in them.
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I see. So you mean the common 2014-12-09 too, right?
What about this guy:
http://www.ebay.com/itm/Symmetricom-Inside-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-GPS-Ant-/181948031179?hash=item2a5cf2a0cb:g:rlcAAOSwyQtVkpxI (http://www.ebay.com/itm/Symmetricom-Inside-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-GPS-Ant-/181948031179?hash=item2a5cf2a0cb:g:rlcAAOSwyQtVkpxI)
Anyone know anything about that one?
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Also, make sure you get one with the type if output you want - square or sine
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This should be the same board they are using inside the box:
https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-%28ocxo-furuno-receiver%29/ (https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-%28ocxo-furuno-receiver%29/)
Seems to work fine, uses a boost converter for the OCXO which doesn't seem overly reliable.
If don't mind a larger box and a potentially less sensitive GPS receiver also check out the surplus Nortel NTBW50AA offerings on ebay. They don't give 1 PPS without a mod but they are a very nice unit and they work with LadyHeather.
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Also, make sure you get one with the type if output you want - square or sine
Not that these are terribly expensive if I get the "wrong" output type, but what would drive one to pick sine- or square-wave output?
I can imagine that phase locking an analog oscillator to the sine-wave output might be more robust. Similarly, generating an integer-ratio digital clock from the square-wave output seems like it might be more accurate as there would not be a need for a comparator to trigger the logic.
There's also the harmonic content of the square-wave output that could either be considered as either an advantage (markers up in frequency, for example) or a disadvantage.
I don't know what test equipment generally requires/desires, such as RF signal generators. I checked what I could find on a Marconi 2022x (for example) and only found that it "accepts a 10 MHz signal of at least 1 V (max. 2 V) into a 100 Ohm nominal impedance. A 5 MHz or 1 MHz signal can be accepted by changing an internal link." Is there any common preference for waveform shape among generators and the like that are newer than the analog boat-anchors?
Is there something that I'm missing about output waveform that I should consider before I commit to one of these?
Edit: Is the "square-wave" unit simply a sine-wave oscillator with a comparator internal to the GPSDO box?
At least looking at http://www.morion-us.com/catalog_pdf/MV89.pdf (http://www.morion-us.com/catalog_pdf/MV89.pdf) it looks like the OCXO is sine-wave output.
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That's a very good question, Jeff. I've wondered the same thing as the external clock inputs on counters that I've seen also specify amplitude and frequency, but not waveform type.
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Couldn't you run the 10mhz square through a 10mhz filter yo get the sine wave.
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Yep. Trim off the harmonics.
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Couldn't you run the 10mhz square through a 10mhz filter yo get the sine wave.
Yes, but you will introduce phase noise when you do this. Personally I prefer the sine output, and if I really need to square it up, I can run it through a schmidtt trigger. The two pieces of test equipment I'm using this with don't seem to have an issue accepting a sine input, so I haven't had to do this.
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I figured that since in the lucent boxes they would run the oscillator through a filter to get the 15mhz. That it should work. Other than that i have seen it used in digibridges to turn the sine approximation into a sine wave.
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I figured that since in the lucent boxes they would run the oscillator through a filter to get the 15mhz. That it should work. Other than that i have seen it used in digibridges to turn the sine approximation into a sine wave.
It does work. What I have read is that the higher the "Q" of the circuit, the worse the problem. So I guess in theory a LPF would be better than a bandpass filter.
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Hi,
My first post to the group. I've been looking to find a reasonably priced GPSDO and I ended up finding this discussion on the BG7TBL and decided to order one. According to some opinions the 2015-07-08 version with the Oscilloquartz "Star 4" was a particularly good one. I searched and couldn't find that version anywhere so I ordered a new one at about the lowest cost I could find.
What I received was this one listed with the 2015-09-17 date (Version) stamped on the front. Ebay # 331800738725 - It contained the GPSDO, antenna and 12V wall wart.
The GPS is a U-blox NEO-6M-0-001 and the OXCO is a Oscilloquartz 8663-XS dual oven. Reading the stats on the stability, it's pretty tight: http://tinyurl.com/h4j58ea (http://tinyurl.com/h4j58ea)
One of the reasons for my posting this is the master chart on the first page reflects the oven to be a morion mv201 but this one is Oscilloquartz but not the same one pictured in the shots of the "Star 4". The specs on this one are better than the morion mv201.
Thanks for the previous inputs to the discussion, it helped me decide to give the BG7TBL a go.
Gary
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Hi,
My first post to the group. I've been looking to find a reasonably priced GPSDO and I ended up finding this discussion on the BG7TBL and decided to order one. According to some opinions the 2015-07-08 version with the Oscilloquartz "Star 4" was a particularly good one. I searched and couldn't find one anywhere so I ordered one at about the lowest cost I could find.
What I received was this one is listed with the 2015-09-17 date (Version) stamped on the front. Ebay # 331800738725 - It contained the GPSDO, antenna and 12V wall wart.
The GPS is a U-blox NEO-6M-0-001 and the OXCO is a Oscilloquartz 8663-XS dual oven. Reading the stats on the stability, it's pretty tight: http://tinyurl.com/h4j58ea (http://tinyurl.com/h4j58ea)
One of the reasons for my posting this is the master chart on the first page reflects the oven to be a morion mv201 but this one is Oscilloquartz but not the same one pictured in the shots of the "Star 4". The specs on this one are better than the morion mv201.
Thanks for the previous inputs to the discussion, it helped me decide to give the BG7TBL a go.
Gary
do you have pictures you can share?
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Hi,
My first post to the group. I've been looking to find a reasonably priced GPSDO and I ended up finding this discussion on the BG7TBL and decided to order one. According to some opinions the 2015-07-08 version with the Oscilloquartz "Star 4" was a particularly good one. I searched and couldn't find one anywhere so I ordered one at about the lowest cost I could find.
What I received was this one is listed with the 2015-09-17 date (Version) stamped on the front. Ebay # 331800738725 - It contained the GPSDO, antenna and 12V wall wart.
The GPS is a U-blox NEO-6M-0-001 and the OXCO is a Oscilloquartz 8663-XS dual oven. Reading the stats on the stability, it's pretty tight: http://tinyurl.com/h4j58ea (http://tinyurl.com/h4j58ea)
One of the reasons for my posting this is the master chart on the first page reflects the oven to be a morion mv201 but this one is Oscilloquartz but not the same one pictured in the shots of the "Star 4". The specs on this one are better than the morion mv201.
Thanks for the previous inputs to the discussion, it helped me decide to give the BG7TBL a go.
Gary
do you have pictures you can share?
Hi, I tried to get good ones but can't find my camera so am offering these from my cell phone. It takes lousy close-up photos so these are the best photos I can get right now.
I see the circuit board is a newer date of 2015-11-24 so that means they're now using older covers with newer boards.
Can't compare it to other boards/versions but it seems to work just fine. Using the uBlox software from here -> https://www.u-blox.com/en/product/u-center-windows (https://www.u-blox.com/en/product/u-center-windows), it seems to be locked on and FWIW, I'm most happy with the frequency stability with my radio in narrow modes.
Next project is to figure out how to use the BG7TBL to keep my computer clock on time in Win 10
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Looks nice and tidy on the inside, kinda hate the ones with hacks, it would just bother my OCD to much.
I don't own a gpsdo, dont really have any legitimate reason to have one, but want one anyway. Knowing frequency/timing measurements could be fractionally more accurate, and my scope and SA have 10mhz inputs, all connectors need to be used...must resist.
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Can't compare it to other boards/versions but it seems to work just fine. Using the uBlox software from here -> https://www.u-blox.com/en/product/u-center-windows (https://www.u-blox.com/en/product/u-center-windows), it seems to be locked on and FWIW, I'm most happy with the frequency stability with my radio in narrow modes.
So the serial port is directly connected to the UBlox? Is there another processor on the board?
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Can't compare it to other boards/versions but it seems to work just fine. Using the uBlox software from here -> https://www.u-blox.com/en/product/u-center-windows (https://www.u-blox.com/en/product/u-center-windows), it seems to be locked on and FWIW, I'm most happy with the frequency stability with my radio in narrow modes.
So the serial port is directly connected to the UBlox? Is there another processor on the board?
Unfortunately, I have no idea. Perhaps the chips in the photos can answer that? They don't provide any block diagram or paperwork of any kind with the unit but; connecting the RS232 to USB cable to the BG7TBL and the other to the USB port in the computer and by selecting the open port seen in the receiver setup in the uBlox software, gives me the data on the graph I posted above.
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Can't compare it to other boards/versions but it seems to work just fine. Using the uBlox software from here -> https://www.u-blox.com/en/product/u-center-windows (https://www.u-blox.com/en/product/u-center-windows), it seems to be locked on and FWIW, I'm most happy with the frequency stability with my radio in narrow modes.
So the serial port is directly connected to the UBlox? Is there another processor on the board?
Unfortunately, I have no idea. Perhaps the chips in the photos can answer that? They don't provide any block diagram or paperwork of any kind with the unit but; connecting the RS232 to USB cable to the BG7TBL and the other to the USB port in the computer and by selecting the open port seen in the receiver setup in the uBlox software, gives me the data on the graph I posted above.
Ok, I suspect it's like several of the other BG7TBL designs. There is an 8-bit micro on there which is communicating with the uBlox chip. The RS232 cable is connected. via a MAX232, to the Tx of the uBlox chip. So the PC can listen to the uBlox data, but not configure it at all (because the 8-bit micro is connected to the uBlox Rx). It's an OK set-up for most people's needs.
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Has anyone tried the BG7TBL distribution amp?
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I've tried unsuccessfully, to find a software to sync the BG7TBL with my computer. I've tried all that I could find and none of them work properly, some made the date crazy as in month 25 in year 1999 & 2025. The U-Blox "U-Center" displays an accurate clock but there's no method to sync it to the computer.
Any suggestions of a software that works with Windows?
Thanks.
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I've tried unsuccessfully, to find a software to sync the BG7TBL with my computer. I've tried all that I could find and none of them work properly, some made the date crazy as in month 25 in year 1999 & 2025. The U-Blox "U-Center" displays an accurate clock but there's no method to sync it to the computer.
Any suggestions of a software that works with Windows?
Thanks.
I think you could attach it to a Raspberry Pi set up to be an NTP server, and then configure Windows to sync with that NTP server. Here is one article discussing using the RPi + a GPSDO as an NTP server:
http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html (http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html)
Windows has built-in support for syncing with an NTP server.
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I've tried unsuccessfully, to find a software to sync the BG7TBL with my computer. I've tried all that I could find and none of them work properly, some made the date crazy as in month 25 in year 1999 & 2025. The U-Blox "U-Center" displays an accurate clock but there's no method to sync it to the computer.
Any suggestions of a software that works with Windows?
Thanks.
I think you could attach it to a Raspberry Pi set up to be an NTP server, and then configure Windows to sync with that NTP server. Here is one article discussing using the RPi + a GPSDO as an NTP server:
http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html (http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html)
Windows has built-in support for syncing with an NTP server.
I very much appreciate the reply.
First, I wanted the GPSDO to maintain the maximum frequency stability with my radio and to this end, that has been accomplished.
2nd, I've had lousy luck getting windows to sync properly. For whatever reason, it can't seem to reach their servers. As I'm not using a firewall other than native Windows 10 firewall, it should go right through. I really don't have to have the ultra close tolerance of time the GPSDO provides but I have found my computer strays a few seconds/day and if I don't keep it constantly adjusted it affects my log time in ham radio and that of contest start and stops. Having the proper time within a second is necessary for me in this regard. The old Windows adjustment was more obvious with the seconds being easy to work with, win 10 was made by people on a bad day.
3rd, Its frustrating that literally every single software that claims to sync your computer with a GPS that I have found, has failed to sync and most often, can't even find the satellites even when I put in parameters that other software accepts and finds them instantly. Not one software both IDs the satellites and syncs. So I have tried many different NTP programs and the one that always worked was the one from NIST but it had to be manually started each time I ran windows, a PITA. I finally found NetTime http://www.timesynctool.com/ (http://www.timesynctool.com/) an open source tool which syncs with an NTP server and corrects the time every 15 minutes. I would have rather synced via satellite but till I find something that works as advertised, this will have to do.
Thanks again for the reply and for suggesting a workable solution!
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I've tried unsuccessfully, to find a software to sync the BG7TBL with my computer. I've tried all that I could find and none of them work properly, some made the date crazy as in month 25 in year 1999 & 2025. The U-Blox "U-Center" displays an accurate clock but there's no method to sync it to the computer.
Any suggestions of a software that works with Windows?
Thanks.
I think you could attach it to a Raspberry Pi set up to be an NTP server, and then configure Windows to sync with that NTP server. Here is one article discussing using the RPi + a GPSDO as an NTP server:
http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html (http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html)
Windows has built-in support for syncing with an NTP server.
I very much appreciate the reply.
First, I wanted the GPSDO to maintain the maximum frequency stability with my radio and to this end, that has been accomplished.
2nd, I've had lousy luck getting windows to sync properly. For whatever reason, it can't seem to reach their servers. As I'm not using a firewall other than native Windows 10 firewall, it should go right through. I really don't have to have the ultra close tolerance of time the GPSDO provides but I have found my computer strays a few seconds/day and if I don't keep it constantly adjusted it affects my log time in ham radio and that of contest start and stops. Having the proper time within a second is necessary for me in this regard. The old Windows adjustment was more obvious with the seconds being easy to work with, win 10 was made by people on a bad day.
3rd, Its frustrating that literally every single software that claims to sync your computer with a GPS that I have found, has failed to sync and most often, can't even find the satellites even when I put in parameters that other software accepts and finds them instantly. Not one software both IDs the satellites and syncs. So I have tried many different NTP programs and the one that always worked was the one from NIST but it had to be manually started each time I ran windows, a PITA. I finally found NetTime http://www.timesynctool.com/ (http://www.timesynctool.com/) an open source tool which syncs with an NTP server and corrects the time every 15 minutes. I would have rather synced via satellite but till I find something that works as advertised, this will have to do.
Thanks again for the reply and for suggesting a workable solution!
I've observed the behavior that you describe w.r.t. Windows being a bit out of sync with the configured time servers. I'm not sure what the behavior is in Windows 10, but I believe in Windows 7 and earlier the time synchronization only runs once per week! For server versions of Windows, the typical configuration would have the machines synchronizing with a domain controller. I suspect the Windows team was trying to balance load on the time servers. The people operating those were probably quite fearful of tens or hundreds of windows machines all banging on their servers every few minutes.
I do know there were some NTP-related improvements in Windows 10. That web site I linked to earlier has a fair amount of info on setting up NTP on Windows. I would take a look there, and maybe even email the owner.
http://www.satsignal.eu/ntp/Win-7_to_Win-10_upgrade.html (http://www.satsignal.eu/ntp/Win-7_to_Win-10_upgrade.html)
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Have you looked at the standard NTPD package? I don't know if there is a reference clock that understands U-blox binary format, but you might be able to find something.
I believe that there are also registry hacks to modify the operation of Windows built-in NTP client.
Ed
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Have you looked at the standard NTPD package? I don't know if there is a reference clock that understands U-blox binary format, but you might be able to find something.
I believe that there are also registry hacks to modify the operation of Windows built-in NTP client.
Ed
AFAIK, the output from the BG7TBL units with UBlox are standard NMEA text strings. There will also be some Ublox specific ones in there, but it should all be text strings in NMEA format and those should just get ignored by the software.
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Oh, also make sure the Windows Time Service is set to run continuously. In services.msc, the Startup Type should be "Automatic". Looks like it is set to Manual by default, and is probably triggered periodically by some scheduled task. Once you've done that, this page has some info on using the w32tm utility to configure Windows to sync against a particular NTP server(s). You can point it at the RPi NTP server on your local network. There is also an example showing how to configure a laptop to sync from one server when it's available, but from an Internet server when it's not.
http://support.ntp.org/bin/view/Support/WindowsTimeService (http://support.ntp.org/bin/view/Support/WindowsTimeService)
Once this is set up, you can run "w32tm /resync" to force Windows to start an immediate synchronization with the time server. However, it may take some time for things to actually sync up, because the OS will try and speed up or slow down the clock to gradually bring things into sync (it doesn't abruptly change the time). You can use "w32tm /query /status /verbose" to get some info on where this process is at.
Note, I found all this by searching and reading various articles online. Although I work for Microsoft, I don't have any contacts in the team that owns this. I will see if I can find someone that knows a bit more about this to validate the info I've provided here.
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AFAIK, the output from the BG7TBL units with UBlox are standard NMEA text strings. There will also be some Ublox specific ones in there, but it should all be text strings in NMEA format and those should just get ignored by the software.
Okay, I assumed that the output would be U-blox binary. If it's NMEA, then there's an NTP reference clock that understands NMEA. Should be easy to use NTPD to keep the PC clock on time and/or turn that PC into a Stratum 1 NTP server.
Ed
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Ok, I have Windows synchronizing with an NTP server reliably now. Here is how I have set things up. I am running Windows 10, but I think this should work with previous versions of Windows.
1) Set Windows Time Service to run continuously. Click Start/Run and enter "services.msc". This should open the Services control panel applet. Scroll down to "Windows Time", right click, select "Properties" in the pop-up menu, and in the properties window change "Startup type" to either "Automatic" or "Automatic (Delayed Start)". Click OK to save your changes.
2) Configure the time service to point to your NTP server. I am using a remote NTP server in the example below, but if you've set up a local NTP server linked to your GPSDO, you should use the IP address or hostname of that in this command. Open a Administrative CMD prompt and enter this:
w32tm /config /update /manualpeerlist:"0.pool.ntp.org,0x8 1.pool.ntp.org,0x8 2.pool.ntp.org,0x8 3.pool.ntp.org,0x8" /syncfromflags:MANUAL
Here we have configured the system with 4 different NTP servers, (0.pool.ntp.org, 1.pool.ntp.org, etc). It will pick one, and use the others in the event the primary server is not available. The ",0x8" on the end of the server name is a flag to tell it to operate in NTP client mode (see NTP docs on this, but this is what you want). The /syncfromflags:MANUAL tells it to use the servers in the manualpeerlist. If your computer is on the domain, you would instead use /syncfromflags:MANUAL,DOMHIER. This will tell the time service to use the local domain controller if it's available, but to fall back to the ntp.org time servers if not (for example if your laptop is not connected to the network with the domain controller).
3) Next we need to change some default settings for the time service. Run "regedit.exe", and change this parameter:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config\MinPollInterval
The default value for Windows machines that are not domain controllers is "10". This means the Windows NTP client will only poll the remove server for time every 2^10 = 1024 seconds. That's fine for most purposes, but it does mean it will take some time for the local time to synchronize up with the NTP server. If you want this process to move along quicker, change it to a lower value like 6 (every 64 seconds). If your not pointing at a local NTP server, I would recommend setting it back to 10 after the initial synchronization is complete.
4) We need to tell the time service to reload configuration. I believe this should work for that, but if not you can go back into services.msc and restart the service:
w32tm /config /update
5) Now let's force the time service to start an immediate resync with this command:
w32tm /resync
You can monitor progress of the resync with this command:
w32tm /query /status /verbose
Here is the output of that command on my desktop:
Leap Indicator: 0(no warning)
Stratum: 2 (secondary reference - syncd by (S)NTP)
Precision: -6 (15.625ms per tick)
Root Delay: 0.0312500s
Root Dispersion: 0.2328713s
ReferenceId: 0x84A30465 (source IP: 132.163.4.101)
Last Successful Sync Time: 3/31/2016 2:02:53 PM
Source: 2.pool.ntp.org,0x8
Poll Interval: 9 (512s)
Phase Offset: -0.7133668s
ClockRate: 0.0156381s
State Machine: 2 (Sync)
Time Source Flags: 0 (None)
Server Role: 0 (None)
Last Sync Error: 0 (The command completed successfully.)
Time since Last Good Sync Time: 44.6045029s
The phase offset of -0.7133668s indicates that my desktop is about 0.7 seconds behind the time reported by the NTP server, 2.pool.ntp.org, during the last sync. This is because it's not done synchronzing yet.
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Well, I down to make two GPSDO, I´ve order 2 MV89a from 2006.
I'll use the G3RUH schematic, but for the MV89 part will use the VE2ZAZ divider.
I was looking for an HP Z3805A, the but shipping is the same price of the HP or more expensive, so I'll pass on that for now.
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Well, I down to make two GPSDO, I´ve order 2 MV89a from 2006.
I'll use the G3RUH schematic, but for the MV89 part will use the VE2ZAZ divider.
I was looking for an HP Z3805A, the but shipping is the same price of the HP or more expensive, so I'll pass on that for now.
Could you share details on the "VE2ZAZ divider"? I am not familiar with that.
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Also - back on the Windows NTP client topic - one of my coworkers suggested the Meinberg NTP Server. After installing it, he disables the built-in time server sync with:
w32tm /config /syncfromflags:no
Then forces a sync and starts the NTP service with these commands:
ntpdate -b pool.ntp.org
net start ntp
https://www.meinbergglobal.com/english/sw/ntp.htm (https://www.meinbergglobal.com/english/sw/ntp.htm)
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The software from Meinberg is actually the standard NTPD package. They just have a convenient Windows binary and installer. You can configure it as a client or server.
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The software from Meinberg is actually the standard NTPD package. They just have a convenient Windows binary and installer. You can configure it as a client or server.
I installed it earlier today. The installer is great, and even took care of disabling the standard windows time service. It synced up almost immediately.
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Could you share details on the "VE2ZAZ divider"? I am not familiar with that.
It's an divider use for the MV89a, the PDF is here < http://www.ve2azx.net/technical/MV89A-1.pdf (http://www.ve2azx.net/technical/MV89A-1.pdf) >
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I recently bought a BG7TBL GPSDO version 2015-09-17, it has uBlox NEO-6 GPS and Oscilloquartz 8663-XS OCXO.
A neat little unit but some problems with it:
1. you cannot send RS232 data to the GPS, it looks like the GPS is receiving commands from a controller on the board. Some of the commands are invalid because the NMEA output includes error messages. That means you're stuck with the default settings, you can't adjust the GPS parameters or PPS width. That's a pity because the uBlox has a well documented and useful command set.
2. The 10MHz output is actually close to 9999999.9991 Hz, as measured against two other known reliable GPSDO. This defect renders it useless for most applications, the whole point of a 10MHz GPS locked oscillator is that it is GPS locked! Actually it appears locked but has some systematic error, perhaps a software defect in the firmware? Lock is confirmed because the 10MHz output shows a periodic (about 2.89 Hz) timing variation of amplitude around 10nS. This is typical of a working locked GPSDO. But the average frequency should be 10MHz exactly, otherwise it is useless.
No problem if you just want NMEA and PPS, but in that case you wouldn't have bought a GPS with an OCXO for 3 times the cost of the GPS alone.
I wonder if anyone has a solution for this bug?
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I recently bought a BG7TBL GPSDO version 2015-09-17, it has uBlox NEO-6 GPS and Oscilloquartz 8663-XS OCXO.
A neat little unit but some problems with it:
1. you cannot send RS232 data to the GPS, it looks like the GPS is receiving commands from a controller on the board. Some of the commands are invalid because the NMEA output includes error messages. That means you're stuck with the default settings, you can't adjust the GPS parameters or PPS width. That's a pity because the uBlox has a well documented and useful command set.
2. The 10MHz output is actually close to 9999999.9991 Hz, as measured against two other known reliable GPSDO. This defect renders it useless for most applications, the whole point of a 10MHz GPS locked oscillator is that it is GPS locked! Actually it appears locked but has some systematic error, perhaps a software defect in the firmware? Lock is confirmed because the 10MHz output shows a periodic (about 2.89 Hz) timing variation of amplitude around 10nS. This is typical of a working locked GPSDO. But the average frequency should be 10MHz exactly, otherwise it is useless.
No problem if you just want NMEA and PPS, but in that case you wouldn't have bought a GPS with an OCXO for 3 times the cost of the GPS alone.
I wonder if anyone has a solution for this bug?
My understanding is that this bug (http://www.ke5fx.com/gpscomp.htm) was fixed recently. How long ago did you purchase yours, and is 2015-09-17 the latest firmware?
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My understanding is that this bug was fixed recently. How long ago did you purchase yours, and is 2015-09-17 the latest firmware?
Thanks a lot. I'm very glad there's a fix, mine was bought late February so will not have the updated firmware. Now I will try to contact the manufacturer. The OCXO looks pretty decent so it would be nice to have firmware that does justice to it.
It may seem like a small error, but when using it to measure the phase of a 39062.5 Hz signal to 0.1 degree accuracy, it drifts by -32 degrees in seven hours. No good at all!
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My first post Hello Guys.
I too have access to recent BG7TBL GPSDO.
I thought of using to clocktame SDR but this GPSDO gives 10M OUTPUT :SINE WAVE,1Vrms (10-15dBm) and square wave,3.3/4.7Vpp.
And all SDRs mostly required cmos square wave for CLKIN. It requires some converter from sine/square to cmos square wave.
Like Si5338/Si5351 programmable clock can be used to take reference from GPSDO and can generate many different frequency CMOS output.
https://www.silabs.com/Support%20Documents/TechnicalDocs/Si5338.pdf (https://www.silabs.com/Support%20Documents/TechnicalDocs/Si5338.pdf)
https://www.silabs.com/Support%20Documents/TechnicalDocs/Si5351-B.pdf (https://www.silabs.com/Support%20Documents/TechnicalDocs/Si5351-B.pdf)
Also make sure to re-confirm square/sine output of this GPSDO.Sometime it doesn't matter whether you ordered square or sine,you can get any.
Dhiru
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For you guys that have had these BG7TBL's for awhile, how are they holding up? Maybe cheaper than designing my own, why reinvent the wheel!
I'm thinking about the latest one 2015-09-17 with the Morion 89A OCXO.
Thanks,
Rob
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Wow. Lots of info! Anyone know what the best model to get for use in a basement? It sounds like the Oscilloquarz would have been the way to go, but these do not seem to be available anymore.
Thanks.
none of them are likely to run from the basement. you'll need to run an antenna outside. so it won't really matter which one you get.
bg7tbl has a newer revision of the morion/ublox, which may fix the counter bug. but realistlcally speaking even with the "buggy" one the error is so small as to be largely irrelevant for hobbyist needs.
I just checked with an eBay seller and the "latest version" (2015-09-17). I asked if he had the fix in and he said no.(May 1, 2016)
Rob
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Wow. Lots of info! Anyone know what the best model to get for use in a basement? It sounds like the Oscilloquarz would have been the way to go, but these do not seem to be available anymore.
Thanks.
none of them are likely to run from the basement. you'll need to run an antenna outside. so it won't really matter which one you get.
bg7tbl has a newer revision of the morion/ublox, which may fix the counter bug. but realistlcally speaking even with the "buggy" one the error is so small as to be largely irrelevant for hobbyist needs.
I just checked with an eBay seller and the "latest version" (2015-09-17). I asked if he had the fix in and he said no.(May 1, 2016)
Rob
Hi
One gotcha may be that the older boards and the newer ones have minor hardware changes between them. You certainly see jumper wires on some of the early ones ... I have not seen a "new" one.
Bob
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Don't know. He did give me the option of the Oscilloquartz 8663 or Morion MV62 OCXO, by the way.
Rob
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Does anybody have a copy of the fixed firmware, surely it can't be hard to update.
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Does anybody have a copy of the fixed firmware, surely it can't be hard to update.
Hi
I think the practical answer is to spend some quality time on the internal Chinese ham forums. That's where most of the up to date information on all of the BG7TBL stuff is.
Bob
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1st: Here is a (the) manual for the BG7TBL GPSDO. Its "offical", because i got it from BG7TBL directly with the permission to "publish" it :-+ Its a mixed language version: Chinese/English.
http://docdro.id/EA3BHpD (http://docdro.id/EA3BHpD)
2nd: A fix for that small frequency "bug" discovered earlier (KE5FX) is been tested right now as mentioned by BG7TBL Testing will go on for several months (!) and a firmware update will be available after that. A fix is not yet available as told by BG7TBL.
http://www.directupload.net/file/d/4368/fhuiqra4_jpg.htm (http://www.directupload.net/file/d/4368/fhuiqra4_jpg.htm)
Note: None of the available variants of the BG7TBL GPSDO, which have been affected by this timing "bug", have a bug fix yet, not even the latest version and their variants dated 2015-09-17.
I hope this will help.
PS.: - I tried to "improve" somehow on the English side of the manual to make it more comprehensible and came up with this slightly modified version http://docdro.id/DrXNab8 (http://docdro.id/DrXNab8)
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1st: Here is a (the) manual for the BG7TBL GPSDO. Its "offical", because i got it from BG7TBL directly with the permission to "publish" it :-+ Its a mixed language version: Chinese/English.
http://docdro.id/EA3BHpD (http://docdro.id/EA3BHpD)
2nd: A fix for that small frequency "bug" discovered earlier (KE5FX) is been tested right now. Testing will go on for several months (!) and a firmware update will be available after that. A fix is not yet available as told by BG7TBL.
http://www.directupload.net/file/d/4368/fhuiqra4_jpg.htm (http://www.directupload.net/file/d/4368/fhuiqra4_jpg.htm)
Note: None of the available variants of the BG7TBL GPSDO have a bug fix yet, not even the latest version and their variants dated 2015-09-17.
I hope this will help.
Hi
The testing for any GPSDO firmware mod often goes into the many months to maybe a year range. There are very few ways to speed up checking a very long time constant control loop.
Bob
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Note: None of the available variants of the BG7TBL GPSDO have a bug fix yet, not even the latest version and their variants dated 2015-09-17.
not all of the variants have the bug.
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Hi
I think the practical answer is to spend some quality time on the internal Chinese ham forums. That's where most of the up to date information on all of the BG7TBL stuff is.
Bob
Do you have a link to these forums? Thank you.
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Hi
I think the practical answer is to spend some quality time on the internal Chinese ham forums. That's where most of the up to date information on all of the BG7TBL stuff is.
Bob
Do you have a link to these forums? Thank you.
Hi
Do a search (In Chinese) for BG7TBL. From there you will get into them. If you aren't fluent in the language, don't bother. Google Translate gets lost quickly in the tangle of idiomatic speech.
Bob
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Do you know which versions don't have the bug?
Do we know that the current versions with the bug are upgradeable when it is fixed?
I want to buy one but, even though the accuracy with the bug is still better than I need, it would always annoy me to know I had one that is flawed.
Note: None of the available variants of the BG7TBL GPSDO have a bug fix yet, not even the latest version and their variants dated 2015-09-17.
not all of the variants have the bug.
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Do you know which versions don't have the bug?
probably any of the ones based off oscilloquartz or trimble receivers, since the unit is just tapping existing signal sources and not generating brand new ones from scratch.
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This "bug" is supposedly not derived from the type/brand of receiver or OCXO used, but from the internal PLL (?) loop, which seems to "discipline"/pull the OCXO in use to a slight offset compared to the "absolute reference 10 MHz" for unknown reasons (rounding algorithms etc. ?). Thus it might "plague" (almost ?) all versions from my point of view, because it seems to be purely software based.
Even if a revised software will be made available by BG7TBL after finishing his tests, as stated , it is still unknown, how the existing software will be updated with the new version because of programming considerations.
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This "bug" is supposedly not derived from the type/brand of receiver or OCXO used, but from the internal PLL (?) loop, which seems to "discipline"/pull the OCXO in use to a slight offset compared to the "absolute reference 10 MHz" for unknown reasons (rounding algorithms etc. ?). Thus it might "plague" (almost ?) all versions from my point of view, because it seems to be purely software based.
Even if a revised software will be made available by BG7TBL after finishing his tests, as stated , it is still unknown, how the existing software will be updated with the new version because of programming considerations.
no.
the oscilloquartz star based models for 100% certain do not have this bug. there is no pll involved and no ocxo discipline involved. there are no bg7tbl algorithms involved. bg7tbl isn't synthesizing any frequency nor disciplining any ocxo in these models.
i'll have to check my trimble model but i suspect it is the same.
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As long as separate OCXOs and the U-blox GPS recevers in those GPSDo units are involved, there will be a PLL (FLL ?) loop by BG7TBL.
Looking through this thread, with few exceptions almost all GPSDO units done by BG7TBL are build this way, only intermediate deviation from this seem to be those few units sold with complete GPSDO boards from Symmetricom and Trimble some time ago. But they have their weaknesses too, because they are "famous" for their low sensitivity and the rather limited count of satellite channels they will lock onto, which has shown to be problematic for other users with less than ideal GPS antenna situations.
So you gain and loose both ways.
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As long as separate OCXOs and the U-blox GPS recevers in those GPSDo units are involved, there will be a PLL (FLL ?) loop by BG7TBL.
Looking through this thread, with few exceptions almost all GPSDO units done by BG7TBL are build this way, only intermediate deviation from this seem to be those few units sold with complete GPSDO boards from Symmetricom and Trimble some time ago. But they have their weaknesses too, because they are "famous" for their low sensitivity and the rather limited count of satellite channels they will lock onto, which has shown to be problematic for other users with less than ideal GPS antenna situations.
So you gain and loose both ways.
no.
there are no bg7tbl with symmetricom.
the bg7tbl with the oscilloquartz star board uses a u-blox gps and has fantastic sensitivity and will easily lock on to a full constellation. there is no loose with this gpsdo. it's gain all around.
any bg7tbl using the "uccm" board does not have the timing bug, because the uccm simply is a transparent passthrough.
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"2015-09-17" (variant 2 - bliley nvg47a1282)
custom board with surplus bliley nvg47a1282 (http://web.archive.org/web/20160725005042/http://www.mikrocontroller.net/attachment/107430/6891__NVG47A1282_RoHS.pdf) OCXO. gps is u-blox NEO-6M-0-001 (https://www.u-blox.com/en/product/neo-6-series)
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Hi all,
I'm new here and found this board while looking for more information about a GPSDO I bought on eBay. Mine has the Trimble board and OCXO, so I guess it's a variant of "2015-07-17". It's sold by eBay user "amoj1010" and the interface board has the seller ID marked on it. It's a nice box, with two DB9 serial ports -- one shows the UCCM command interface, and the other reports binary location data. I'm attaching some pictures from the eBay listing.
Also, I apologize if this is old news, but I discovered that the commercial software GPSCon Pro can monitor these units! It's not cheap ($77.67) but it works well, and it beats typing in commands at the "UCCM" prompt and deciphering the results. Also attached is a screenshot from GPSCon monitoring my box.
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I'm new here and found this board while looking for more information about a GPSDO I bought on eBay. Mine has the Trimble board and OCXO, so I guess it's a variant of "2015-07-17". It's sold by eBay user "amoj1010" and the interface board has the seller ID marked on it. It's a nice box, with two DB9 serial ports -- one shows the UCCM command interface, and the other reports binary location data. I'm attaching some pictures from the eBay listing.
this gpsdo does not appear to be a variant of bg7tbl. this is a completely independent design.
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Hi,
Does anyone know the normal values temperature on the case surface of morion mv89a OCXO?
There is a suspicion that the oven is faulty.
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Hi,
Does anyone know the normal values temperature on the case surface of morion mv89a OCXO?
There is a suspicion that the oven is faulty.
37C
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A bit of a necro, but this seems to be the right place for it. I picked up one of these BG7TBL GPSDOs on ebay for $140 including a power pack and an antenna, haven't cracked it open yet, but it seems to be working properly and interestingly, there has been another revision labeled 2016-05-31. I got mine from here: http://www.ebay.com/itm/171742240714 (http://www.ebay.com/itm/171742240714)
I've got the NMEA data being read out into VisualGPS (free tracking program), but it doesn't include timing information, and lady heather doesn't seem to want to communicate with it, at least in the standard configuration. Any ideas on software to get a readout of the timing corrections and such - would be fascinating to see. I will crack it open and get some pics, but in the mean time, enjoy the "square" wave it outputs :D *when properly terminated it looks a lot better!*
(http://www.medpants.com/rage/gpsdo.jpg)
More than I expected, it seems to be tracking 9 satellites at the moment.
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Why did you turn it on before taking it apart? :-DD
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As a rule of thumb for ebay stuff from China.... I turn it on first to make sure it runs :-BROKE
Oops, though, I wasn't being fair. The input was still 1M terminated, looks much much nicer with 50 ohms set! Pretty decent rise and fall times and a fairly flat top, though there's a nice little point right after the rise completes.
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A bit of a necro, but this seems to be the right place for it. I picked up one of these BG7TBL GPSDOs on ebay for $140 including a power pack and an antenna, haven't cracked it open yet, but it seems to be working properly and interestingly, there has been another revision labeled 2016-05-31. I got mine from here: http://www.ebay.com/itm/171742240714 (http://www.ebay.com/itm/171742240714)
please crack it open, would be interested to see what's changed - if anything. :-+
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Hopefully these are good enough to be useful, the board looks the same but is marked 2016-05-01 - maybe the 31st is the first time the board was actually built up, maybe there was a part swap in that month. Primary chips are a uBlox Neo-7M-0-000 and a Bliley NVG47A1282 oscillator. The box is solid extruded aluminum and according to the sticker on the back, there is a sine wave output variant, but this is the square wave version. This is the designer's store site: https://bg7tbl.world.taobao.com/ (https://bg7tbl.world.taobao.com/) - the product image reflects this version number, I can't read any of the descriptions though :p
(http://www.medpants.com/rage/gpsdotop.jpg)
(http://www.medpants.com/rage/gpsdobottom.jpg)
Looks like there isn't any timing adjust data being sent out of the thing, but it also doesn't seem like it's just an rs232 interface through to the GPU unit's comms, so maybe there's room for it in firmware. In my brief buzzing out to try to find the serial interface passing to the uBlox module, I found that D2 was an LED.... kinda funny, but there's a blue LED on the underside of the board in the aluminum box that no one will likely see... but it blinks when the GPS locks - looks to be locked to the 1pps output or vice versa. Tracking up to 12 satellites too!
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Hi folks! This is my first post om this forum. I hope my contribution is usefull... Yesterday I received my BG7TBL GPSDO and made some images of the device for my website. (http://www.amateurtele.com (http://www.amateurtele.com) - http://www.amateurtele.com/index.php?artikel=203 (http://www.amateurtele.com/index.php?artikel=203)) And I think the images are here also in the right spot...
I have some other GPSDO projects being built (VE2ZAZ and W5OJM), and as long as the projects aren't finished, this device is ready for use right now. Now its time to turn it on and see if it works. ::)
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And part two...
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Part three.
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Images can say more than thousand words, right?! 8)
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really nice pictures there, well done :-+
i've updated the list.
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This too is my first post on the forum. I've been following the eevblog saga of the BG7TBL for the last few months with hopes of purchasing one when the infamous "bug" is resolved. I notice Amateurtelecom received a unit with a new data code, 2016-05-31, which was dutifully cataloged in the thread. I've been Google searching this new version for several days on any reference as it relates to the bug. So far nothing has surfaced. If it's fixed, I'll order it. I'm reluctant to query an Ebay reseller as I'm not sure I'd get an accurate answer. If anyone has objective evidence one way or another as to the bugs remediation I, and likely others, would appreciate a post. I realize it may take some time. Thanks again for a new found valuable resource (eevblog that is).
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So I've got one of these current version GPSDOs with the more recent ublox module and I've got a good counter, but I only have the one time source (no tbolt or cesium to compare to :P ) so I'm not sure if any testing I can do will be of value. That being said, I've had it running into the front of the counter for about a day now (mainly as a test for the counter's timebase), but I'd be happy to show the graph and statistics after it runs a bit longer.
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So I've got one of these current version GPSDOs with the more recent ublox module and I've got a good counter, but I only have the one time source (no tbolt or cesium to compare to :P ) so I'm not sure if any testing I can do will be of value. That being said, I've had it running into the front of the counter for about a day now (mainly as a test for the counter's timebase), but I'd be happy to show the graph and statistics after it runs a bit longer.
Where did you source the 2016-05-31 version? I've only found it on Chinese sites (taobao.com, etc.). Thanks.
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DaJMasta, I agree without a reference you'd be unable to assess remediation of the bug. Appreciate the response. It may take some time before someone can verify.
steverino, I too had issues locating this new version.
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Where did you source the 2016-05-31 version? I've only found it on Chinese sites (taobao.com, etc.). Thanks.
ebay, from diyelecmall108 http://www.ebay.com/itm/171742240714 (http://www.ebay.com/itm/171742240714)
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Where did you source the 2016-05-31 version? I've only found it on Chinese sites (taobao.com, etc.). Thanks.
ebay, from diyelecmall108 http://www.ebay.com/itm/171742240714 (http://www.ebay.com/itm/171742240714)
Their photos show two different older versions and the description says, "Our GPSDO is newest version,produce at 2015-9-17,include OCXO." So, they sent you the 2016 version from this listing?
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Yep, I got the link from my ebay history and images of my unit are a dozen posts or so above.
Interestingly, I was shipped the square wave version and amateurtelecom's photos are of the sine wave version. The chips near the output the same, but mine is missing a handful of passives between that sot-23-6 and the 10MHz output, so it looks like the output approach is just filtering the square wave output to make a sine out of it, even though the oven has a sine coming out of it.
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Yeah, amateurtelecom has both versions. I guess they just mixed them up. It is funny that the sine version still generates a square and then filters it.
In what equipment does it matter whether the clock input is sine or square? Not that it's hard to convert from one to the other, just curious.
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I'm not entirely sure.... You'd lose a tiny bit of timing precision triggering off of a sine wave, lower slope means variation in trigger level sensitivity can manifest as jitter, but you'd be able to adjust the trigger level to hit different phases of the same signal (or have multiple triggers, maybe?) And if it really mattered and you needed a sine, you could just filter it on the input side and be sure. I've yet to see a piece of an equipment with an input that specifies one or the other, but maybe they exist.
As for the listing, it could be just that it's an old one - I think ebay lets some sellers list an item for up to a year, so maybe they were originally selling the older model and then just didn't notice that it changed or didn't remember to update the description. There seem to be a lot of sellers that sell stuff in a lot of genres, so maybe they don't really know much about it.
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I haven't seen anything that specified sine vs. square, either. Hence, my curiosity.
If anyone has more info, we're keen to know what the deal is on sine vs. square for clock input.
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2nd: A fix for that small frequency "bug" discovered earlier (KE5FX) is been tested right now as mentioned by BG7TBL Testing will go on for several months (!) and a firmware update will be available after that. A fix is not yet available as told by BG7TBL. I hope this will help.
I wonder if the end user will be able to do a firmware update after purchasing?
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It looks like the parts used are off the shelf and the programming header footprints are on the board, just are unpopulated, so I would assume that's a yes.... but I guess one can only wait for official word.
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I just order from diyelecmall108 on ebay. I emailed him first and confirmed that the version that he's selling is 2016-05-31 and not the older version he's showing in the pics.
Ken
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There was a post a while back where GPS Con was used to monitor the GPSDO. I have the 9/17/16 version and am not able to get GPS Con to communicate with the receiver. Any info on settings?
Thansk,
Bill
K1FPV
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OOOOPS ! I just noticed I messed up on the date of the GPSDO version. It is supposed to read 9/17/2015....not 2016. Anyone have luck with any kind of control software?
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Don't know about GPS Con (and a quick google didn't help), but my version is not controllable via the RS232 port, it just sends the NMEA data as text strings. Many programs can read this, I've been using VisualGPS which is a free download - there's also software from the ublox manufacturer (and this is the GPS can that lives in your GPSDO).
So for monitoring it works great, but you don't get access to any of the feedback or control stuff you can get in more advanced units.
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Thanks for the reply. I've tried Visual GPS View to read the data, but unfortunately, it merely prints Hieroglyphics as does Hyper-terminal. I'd just like to see my location coordinates etc as well as the satellites I'm receiving but I guess it is a lost cause with these low end receivers that just output the NMEA data in hieroglyphic form. :(
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Try changing baud settings, the default for this unit is 9600. When I let my computer go to sleep with the GPSDO connected, when I wake it, all the data coming in is garbled until I reconnect from the menu.
If that fails, maybe try some other settings, it should be standard RS232 communication.
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Just got a newer version of the GPSDO from BG7TBL and it does receive the data fine with Visual GPS View. It seems like a neat program now that it is working. Too bad the other makes of Chinese GPSDOs won't work with Visual GPS View.
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Just got a newer version of the GPSDO from BG7TBL and it does receive the data fine with Visual GPS View. It seems like a neat program now that it is working. Too bad the other makes of Chinese GPSDOs won't work with Visual GPS View.
If the RS232 connectors can output NMEA sentences on one of the pins. Using U-Center from U-Blox works very well. Lot's of features.
https://www.u-blox.com/en/product/u-center-windows] [url]https://www.u-blox.com/en/product/u-center-windows (http://[url)[/url]
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Just got a newer version of the GPSDO from BG7TBL and it does receive the data fine with Visual GPS View. It seems like a neat program now that it is working. Too bad the other makes of Chinese GPSDOs won't work with Visual GPS View.
If the RS232 connectors can output NMEA sentences on one of the pins. Using U-Center from U-Blox works very well. Lot's of features.
[url]https://www.u-blox.com/en/product/u-center-windows]https://www.u-blox.com/en/product/u-center-windows] [url]https://www.u-blox.com/en/product/u-center-windows (http://[url=https://www.u-blox.com/en/product/u-center-windows)[/url]
how about https://www.u-blox.com/en/product/u-center-windows (https://www.u-blox.com/en/product/u-center-windows)
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how about https://www.u-blox.com/en/product/u-center-windows (https://www.u-blox.com/en/product/u-center-windows)
Sorry about the messed up URL, Win 10 and Edge Browser doesn't seem to play nice with the EEVBLOG forum.
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without the proprietary oscilloquartz configuration manager software you wouldn't be able to talk to the ocxo anyway. the protocol does not appear to be documented. nor does the software appear to be available anymore.
I recently got in one of the Oscilloquartz Star-4 GPSDOs off of Ebay:
http://www.ebay.com/itm/10Mhz-GPSDO-OSCILLOQUARTZ-OSA-OEM-GPS-GPSDO-10MHz-1PPS-STAR-GPS-Clock-/262675973538?hash=item3d28b545a2:g:sbYAAOSwh2xYAjrp (http://www.ebay.com/itm/10Mhz-GPSDO-OSCILLOQUARTZ-OSA-OEM-GPS-GPSDO-10MHz-1PPS-STAR-GPS-Clock-/262675973538?hash=item3d28b545a2:g:sbYAAOSwh2xYAjrp)
The serial port output on the unit is a NMEA output stream from the Ublox receiver. I don't think it has a serial input to the GPS.
The GPSDO board is mated to a well built board with a DC-DC converter and RS-232 interface. The 26-pin connector to the GPSDO is broken out to through-hole pads. On the connector is "management interface" serial link. The TX and RX management interface pins (3.3V, 9600 baud serial) are further broken out to some more pads. On the 26-pin connector pin 5A is serial data to the GPSDO, 5B is data from the GPSDO.
I got hold of some documentation for the Star-4 (still checking to see if I can share it).
I connected a RS-232 level converter to those pins and now have Lady Heather talking to it.
The control language lets you adjust the GPSDO time constant, satellite elevation mask, cable delay, enter/exit holdover, warm/cold start. You can monitor device status, alarms, satellite constellation, time/date/position, temperature. There are no messages that indicate things like the PPS time error / oscillator frequency / GPSDO performance.
The device saves the settings/configuration in EEPROM, but always does a 4-hour self-survey on power-up. It takes 10-15 minutes for the device to warm up and the GPSDO PLL to lock.
The next version of Lady Heather (with New and Improved Documentation (tm)) should be out in a couple of week...
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I got hold of some documentation for the Star-4 (still checking to see if I can share it).
I compared my Star-4 documentation to the Star-4 doc posted earlier in this thread and they are pretty much the same. My documentation mentions an INPUT_TYPE(1) command that the other does not talk about (and the device does not respond to anyway), so no need to post it.
Anyway, Lady Heather now talks to and can control the Star-4 serial management port.
The time code that the INFO_GPS_POS; message reports has some occasional skips/duplicates, but Lady Heather tweaks them so the clock displays run smoothly.
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Interesting! Have you tried Lady Heather with other GPSDOs made in China? I've got 3 others that I can't get to talk with PUTTY, Termite, or Visual GPS. I haven't tried SatStat or GPSCon. I love the way the BG7TBL GPSDO communicates with Visual GPS.
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Interesting! Have you tried Lady Heather with other GPSDOs made in China? I've got 3 others that I can't get to talk with PUTTY, Termite, or Visual GPS. I haven't tried SatStat or GPSCon. I love the way the BG7TBL GPSDO communicates with Visual GPS.
Yes, Lady Heather now talks to pretty much all GPSDO, GPS timing receivers, NMEA receivers, GPSD, etc including those small Trimble/Symmetricom "UCCM" GPSDOs.
Attached is a screen dump of Lady Heather controlling the BG7TBL GPSDO via the Star-4 "management" port. It shows the unit doing its 4-hour self-survey after a power-up. Once it surveys in, it switches to position hold mode.
I wired a RS-232 level converter to the management port pins on the 26 pin Star-4 connector. The management port lets you monitor and control the device a lot better than through the NMEA TOD output on the RS-232 connector. One funky thing that happens if you use the management port is the TOD output switches from NMEA to Ublox binary messages.
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Interesting! Have you tried Lady Heather with other GPSDOs made in China? I've got 3 others that I can't get to talk with PUTTY, Termite, or Visual GPS. I haven't tried SatStat or GPSCon. I love the way the BG7TBL GPSDO communicates with Visual GPS.
Yes, Lady Heather now talks to pretty much all GPSDO, GPS timing receivers, NMEA receivers, GPSD, etc including those small Trimble/Symmetricom "UCCM" GPSDOs.
Attached is a screen dump of Lady Heather controlling the BG7TBL GPSDO via the Star-4 "management" port. It shows the unit doing its 4-hour self-survey after a power-up. Once it surveys in, it switches to position hold mode.
I wired a RS-232 level converter to the management port pins on the 26 pin Star-4 connector. The management port lets you monitor and control the device a lot better than through the NMEA TOD output on the RS-232 connector. One funky thing that happens if you use the management port is the TOD output switches from NMEA to Ublox binary messages.
It would be cool if someone stuck their GPSDO into a case with a front panel LCD, with that as the output being displayed.
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It would be cool if someone stuck their GPSDO into a case with a front panel LCD, with that as the output being displayed.
Lady Heather runs well on a Raspberry Pi (also Windows, Linux, macOS). The standard PI LCD display (800x480) can work but is really a a bit too small to be effective. A 1024x768 screen would be a lot better. Linux and macOS use X11 as the display system.
It can work with NMEA, Trimble TSIP, Motorola, Ublox, Sirf, NVS, Z38xx (SCPI), Star-4, GPSD, etc devices or as a fancy clock display off the system clock and provides full control and monitoring/logging.
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You could use a raspberry PI 3 and Yocto to have Lady Heather run on boot.
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It would be cool if someone stuck their GPSDO into a case with a front panel LCD, with that as the output being displayed.
Lady Heather runs well on a Raspberry Pi (also Windows, Linux, macOS). The standard PI LCD display (800x480) can work but is really a a bit too small to be effective. A 1024x768 screen would be a lot better. Linux and macOS use X11 as the display system.
It can work with NMEA, Trimble TSIP, Motorola, Ublox, Sirf, NVS, Z38xx (SCPI), Star-4, GPSD, etc devices or as a fancy clock display off the system clock and provides full control and monitoring/logging.
I bought the same unit as yours. I'll get the raspberry PI 3 running Yocto embedded and Lady Heather.
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How do you get Lady Heather to talk to Ublox, and what version do you use?
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Sorry, actually MTK3339.
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Sorry, actually MTK3339.
The MTK3339 outputs standard NMEA sentences which Heather understands.
For NMEA devices, Heather does not generally attempt to identify the receiver type and issue any proprietary device-specific commands. There are a couple of NMEA receivers (like the Venus timing receivers) that it does recognize and treat specially.
Heather does have a keyboard menu command for sending user-specified NMEA commands to the device... and automatically adds the leading '$' and proper checksum.
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Too bad Lady Heather is not ported to QT. I have my raspberry pi 3 booting yocto. Going to try and see if I can get the native Lady Heather Linux version to compile.
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Too bad Lady Heather is not ported to QT. I have my raspberry pi 3 booting yocto. Going to try and see if I can get the native Lady Heather Linux version to compile.
If you can unzip a file to a directory and type "make" you can compile it... you will need the x11-dev lib installed. I have the documentation section finished up and hope to get the new code out this weekend...
Other than X11 (or WIN VFX under Windoze) Heather has no external package dependencies to speak of... it's a fundamental part of her charm and sleek and svelte persona... someday even WIN VFX will be dropped (it was used when there was a DOS compatible version of Heather)
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I have not looked at the source code of it. I'm wondering how much effort would it be to port it over to QT?
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I have not looked at the source code of it. I'm wondering how much effort would it be to port it over to QT?
Why?
BTW, there's 63000+ lines of code. Around 10000 are just for the user input interface...
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I have not looked at the source code of it. I'm wondering how much effort would it be to port it over to QT?
I'm hurt, deeply hurt. :-DD
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I have not looked at the source code of it. I'm wondering how much effort would it be to port it over to QT?
I'm hurt, deeply hurt. :-DD
Lady Heather will kiss it and make it all better... then smack the crap out of you... don't ask how I know.
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I've got a question! I have a BG7TBL GPSDO, version 2015-09-17 here. It produces about 2.5 volts of a modified saw-tooth waveform into a 50? load and a lousy looking sine-wave into a high impedance. Does the newer version of 2016-05-31 improve on the waveform or are there any major changes in it's output? I believe the newer version's 10 MHz output is supposedly more accurate.
Thanks,
Bill
K1FPV
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Can't speak to the sine wave output variant, but my square wave output version gave a pretty decent square wave with 50 ohm impedance and a very jagged, overshot one at 1M impedance :) (I think there's a pic of it on the scope a page or two back)
Comparing the boards with the current version sinewave output, it seems like the difference is all passive filtering, so it's a square wave until about a half an inch from the BNC terminal where it's filtered to a sine. You can actually use the alternate oscillator through hole pads to tap into the sinewave directly from the oscillator (which is squared up and sent into the cpld, then which comes out of it and to the output), and a little gain on a decent opamp would yield you a nice signal - the raw signal is something like 1Vpp.
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Interesting point....I tried to hook up the output of my 2015-09-17 BG7TBL GPSDO to my counter which was terminated with a 50? load and the high impedance of my scope and I got the waveform mentioned in the last post I made. I have since tried to run it through the BG7TBL 10 port splitter/amplifier designed to supply the 10 MHz to up to 10 pieces of equipment needing the 10 MHz reference. Now at the input of the splitter/amplifier I get a beautiful sine-wave of about 2.8 volts peak to peak as I do at the output ports on the splitter. I guess it likes the input impedance of the splitter/amplifier.
Bill
K1FPV
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I have not looked at the source code of it. I'm wondering how much effort would it be to port it over to QT?
I'm hurt, deeply hurt. :-DD
Don't be... I was just thinking out loud. Would like to stick the gpsdo and a raspberry pi 3 into a nice case with a 10inch display. Have the unit boot directly into Lady Heather. I got my yocto image built. It boots in about 8 seconds.
I'm just having some fun...
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Would like to stick the gpsdo and a raspberry pi 3 into a nice case with a 10inch display. Have the unit boot directly into Lady Heather. I got my yocto image built. It boots in about 8 seconds.
That should be easy to do without having to mess with the code.
I don't know what the PI likes to see in the way of a start-up script, but something like "change to heather directory" followed by "./heather" Heather loads a "heather.cfg" file where you can set all your heather startup config options.
I haven't looked into what it would take to support a touch screen... Heather processes keystrokes from the window manager loop into a small fifo which it then processes when it has nothing else to do. You would need to display an on-screen keyboard and cram keystrokes into that. Once you have heather configured for your tastes, if you are just using it as a monitoring program, you really don't need a keyboard... in fact there is a command line option for disabling the keyboard and/or mouse.
The official PI LCD is not well suited to heather since it is a bit small. Heather likes 1024x768 screens, 800x600 is OKish. X11 does eat a few lines for the window decoration/top menu bar. I suspect that there are ways for bypassing that and recovering that space...
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WOW! I just received the newest version of the BG7TBL GPSDO with the version date of 2016-05-31 and the output wave is the same sawtooth type waveform but the difference mainly is it the amplitude of the output sawtooth. I'm getting 6.8 volts p/p into a 50? load. NOT BAD !!!
Bill
K1FPV
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OOOPS...that was supposed to be 6.8 volts p/p into a 50 ? load.
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HUH the ohm symbol looks fine when I look at the preview, but winds up as a question mark when it is posted. Anyway, it puts 6.8 volts into 50 ohms.
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How does one get the signal strength plot in the bottom right hand corner of the screenshot above to activate?
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This isn't about the BG7TBL GPSDO, but I managed to buy a Datum Starloc II GPSDO board and the price was right. I hooked it up to 24 volts and it works pretty well. I've no got a rock solid 10 MHz. coming out of it and the Lady Heather GPS program works well with it. It's been hooked up for an hour and it appears to be a 6 channel receiver as I only see the info for 6 satelites, but other than that, I've got good time and frequency lock with it.
Has anyone seen a manual for the Datum Starloc II receivers? Has anyone else managed to work successfully with these receivers?
Bill
K1FPV
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I was tempted to buy a few when they were around 50.00. Then the prices doubled . :-[
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I managed to buy a Datum Starloc II GPSDO board and the price was right. I hooked it up to 24 volts and it works pretty well. I've no got a rock solid 10 MHz. coming out of it and the Lady Heather GPS program works well with it.
Uhhh... that's news to me (unless you have a beta copy of the next release of Lady Heather or a different firmware on the GPSDO than mine).
The Starloc II firmware that I have is an utter turd!. They mess up parsing / sending proper TSIP formatted messages (they don't always escape 0x03 bytes). The satellite positions are all reported as az/el = 0.0/0.0. The TSIP command that the Thunderbolt uses to configure automatically sent messages will lock up the Starloc II). I could go on, but my blood's starting to boil... Oh, the things that I had to do to the Lady Heather code to get that turd half-way working... Awww crap, my head just exploded...
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ROFLMAO..... I'll pick up the pieces of residue from the cranial explosion! ;) I've got Lady Heather running now. I was away from my computer for over 24 hours....Heather is still monitoring the Starloc II fine receiving 8 satellites, giving my exact position....the same my other GPSDOs provide and the UTC time is right on with my GPS clock!
I'm trying to figure out the firmware in the receiver. I just bought this receiver from Stormin Norman on eBay. Even at the price now they are asking, it isn't a bad price considering all I have to do is find a small case to mount the receiver in. Anybody have an idea how I can manage to read the firmware inside the receiver? OH....by the way, I also have Trimble Studio v1.64.0, a beta version and that too locks to the receiver. I suspect this must be some kind of Trimble clone.
Now if I can just manage to find an instruction book for the receiver, I'll be happy as a clam! I have the Thunderbolt monitor program, and that program won't do anything with this receiver.
Bill
K1FPV
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I just bought this receiver from Stormin Norman on eBay.
Now if I can just manage to find an instruction book for the receiver, I'll be happy as a clam!
That's where I got mine... oh, the pain it's caused. I look horrible with a ruptured head. Gotta spend some time and sponge down the walls pretty soon.
Your best bet for a manual is the Thunderbolt manual. The Starloc II tries to implement a basic Thunderbolt emulation, screws quite a bit of it up in various ways, and does not implement all the Thunderbolt commands. Mine seems like a pre-alpha firmware release to me that was banged out by a bunch of drunken code monkeys after a week long bender.
What version information is reported by your StarLoc?
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I'm unable to get data via Lady Heather, but with the Trimble Studio, the only data I'm getting off the receiver is (TC_[ID#]_161204_1802_[TC#].log) which is supposed to be logged by the program from the receiver. I have no idea what that information means.
I've been monitoring the output of the receiver at 10 MHz, and my counter using my Spectracom 8195 Ageless Oscillator is 10.0000000 MHz. The counter reads down to .1 Hz when attached to either of my GPS references. I also have an HP58503A and there is no difference in the frequency readings with either of the references. The counter is a BK Precision 1823A. I just wish I was able to get a monitoring program to see all the data coming from the receiver. With the information I have presently on this receiver, I'd get more by picking my nose! Ooooops....if I did that, my head might cave-in! ;)
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I'm unable to get data via Lady Heather, but with the Trimble Studio, the only data I'm getting off the receiver is (TC_[ID#]_161204_1802_[TC#].log) which is supposed to be logged by the program from the receiver.
I just wish I was able to get a monitoring program to see all the data coming from the receiver.
Version 5 of Lady Heather knows about the quirks of this receiver and can work with it (but the auto-detect receiver type function won't work... you have to tell it you have a Starloc II with the -rxd command line option. Programs that expect a Trimble Thunderbolt probably won't work because one of the commands they send to initialize the device makes the Starloc II shut up.
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Where did you get the version 5 of Lady Heather? I've found version 4, but that is a beta version. I'm using version 3.10 which isn't a beta.
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Where did you get the version 5 of Lady Heather? I've found version 4, but that is a beta version. I'm using version 3.10 which isn't a beta.
I wrote Lady Heather... v5 should be released soon.
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Forgot to mention v5 runs on Windows, Linux, and macOS (OSX)
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I just downloaded V4.0 beta, and it logs everything on this puppy, even gives me a sky view of the sats too.
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I had a brain fart! The one with the sky sat view was the one for the program writer. I realized it when I saw the lat & long as well as altitude were way off. DUH ! |O
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I'm about ready to give up on this piece of c#*p ! The Datum Starloc II is for the birds! After about 36 hours, for some unknown reason, it looses lock with Lady Heather as well as with the Trimble Studio. I'll tell ya one thing, the Trimble Studio works works great with my Thunderbolt as well as with a Nortel GPS system I bought that was taken out of service. It obviously uses Trimble inside.
The BG7TBL version 2016-05-31 GPSDO is terrific. It works well with Visual GPS View as well as U-Center 8.23. U-Center has the better information and looks terrific!
Bill
K1FPV
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U-Center has the better information and looks terrific!
U-Center gets my nod, it works very well on non ublox receivers as long as they can output NMEA.
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Yes, I've got to agree that the U-Blox does a great job as does Visual GPS View but I prefer the format used by U-Blox.
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Lady Heather v 5.00 is working great! I only have the USB cabled hooked up to the GPSDO.
I'll add a shifter to the management pins and try out the full control. Did you wire the management pins to the existing serial port, or just break them out to a separate connection?
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Lady Heather v 5.00 is working great! I only have the USB cabled hooked up to the GPSDO.
I'll add a shifter to the management pins and try out the full control. Did you wire the management pins to the existing serial port, or just break them out to a separate connection?
I'm still wired to the Star-4 management port via an external shifter. I am probably going to wire the management port to his level converter circuit (the signals are those two pins that stick down from his board to the Star-4) and wire the TOD output port to one of the unused drivers in the level converter and send that output to a pin on the DB-9 so that things like NTP have a time code.
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Lady Heather version 5.0 is now available for download from:
http://www.ke5fx.com/heather/readme.htm (http://www.ke5fx.com/heather/readme.htm)
Many thanks to John Miles for hosting the distribution and his work on the Windows installer, PDF documentation file, readme file, and bring an all-around good guy.
Heather now has some proper user documentation. Check the heather.pdf file and/or the comments in the first 3500+ lines of the heather.cpp file. Heather can be compiled for Linux (including the Raspberry Pi) and macOS. Download the heatherx11.zip file and check the readme.txt file for compilation instructions.
There are MANY new features in Heather. One of the main ones is support for many new receiver types. When Heather is started it defaults to attempting to automatically determine the receiver type. You can bypass this and force the receiver type using the new "/rx..." command line options. Some receiver types cannot be auto-detected. Also many receivers power up speaking NMEA and you can enable their native binary language using the /rx commands. Native binary mode gives better information and allows controlling the receiver configuration and settings.
Currently-supported receivers include:
Trimble Thunderbolt and Thunderbolt-E
Acron Zeit WWVB receiver
UCCM - Trimble / Symmetricom GPSDOs
DATUM STARLOC II GPSDO
NEC GPSDO (STAR-4 compatible)
GPSD interface
Jupiter-T (aka Zodiac)
Lucent KS24361 REF0/Z3811A (19200:8:N:1)
Motorola binary format
Generic NMEA receiver
Trimble Resolution T family with odd parity
Sirf binary
Generic Trimble TSIP binary
Ublox UBX binary
Venus mixed binary / NMEA
Nortel SCPI-compatible GPSDOs (NTWB, NTPX, etc.)
Z3801A and compatible SCPI GPSDOs
HP 5xxxx-style SCPI
Oscilloquartz STAR-4 (via the management interface)
NVS binary
PC system clock (no receiver)
After installing Heather, you should edit the heather.cfg file (or the PROPERTIES setting for the desktop icon) for your desired configuration. Everybody should change the "/tz" option for their time zone... it comes set up for the US central time zone. International uses should add a "/b..." command to set their daylight savings time information. On Windows, you can press the "n" key and that will bring up NOTEPAD to edit the file. For the changes to take effect you will need to re-start Heather (or do a "r heather.cfg" keyboard command).
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Lady Heather v 5.00 is working great! I only have the USB cabled hooked up to the GPSDO.
I'll add a shifter to the management pins and try out the full control. Did you wire the management pins to the existing serial port, or just break them out to a separate connection?
I'm still wired to the Star-4 management port via an external shifter. I am probably going to wire the management port to his level converter circuit (the signals are those two pins that stick down from his board to the Star-4) and wire the TOD output port to one of the unused drivers in the level converter and send that output to a pin on the DB-9 so that things like NTP have a time code.
Which level shifter did you use? I wired my TTL to serial shifter to both RX and TX management pins. But I get constant voltage on both pins.
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Which level shifter did you use? I wired my TTL to serial shifter to both RX and TX management pins. But I get constant voltage on both pins.
It's one that I built. Has a DB-9 connector, MAX232A, 3.3 or 5V regulator. Also several connectors for various GPS receivers. I wire all my GPS modules to connect to the "CN06" connector. I'm powering it off the 12VDC output of the DC-DC converter... 3.3V regulator on my converter board.
https://oshpark.com/shared_projects/YPvKgMYa
Did you perhaps swap the TX and RX pins on your level shifter?
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Which level shifter did you use? I wired my TTL to serial shifter to both RX and TX management pins. But I get constant voltage on both pins.
It's one that I built. Has a DB-9 connector, MAX232A, 3.3 or 5V regulator. Also several connectors for various GPS receivers. I wire all my GPS modules to connect to the "CN06" connector. I'm powering it off the 12VDC output of the DC-DC converter... 3.3V regulator on my converter board.
https://oshpark.com/shared_projects/YPvKgMYa
Did you perhaps swap the TX and RX pins on your level shifter?
I thought the samething, so I swapped them. I think the problem is powering the level shifter from 12 volts off one of the pins on the 26 pinouts. I'm probing to see if there is another 3.3volt source I can use. Almost there.
The star-4 is a very nice box. I was really surprised.
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Finished a little project relating to this GPSDO and figured I'd post it here, I made a 4 output distribution amplifier that fits inside the current revision BG7TBL units - any of them with the single board with the one power heatsink will do, but for sure I know it fits in my 2016-05-31 model. I've written up some design concerns, a guide to finding signals to tap off on the board, and a full BoM for the mod/project, and the schematic and PCB design are up on CircuitMaker and are free. The most expensive parts of the mod, by far, are the BNCs.
http://medpants.com/distribution-amplifier (http://medpants.com/distribution-amplifier)
It's basically some schmitt triggers and a little filtering if you want sine output, but it can give you any combination of sine or square wave outputs on the board from either a sine or square wave output model GPSDO, if that is useful to you. If you're interested in building up one for yourself, I had to order 10 boards when I had it made, so I can mail a few out for the cost of postage.
The finished one looks like this: (http://medpants.com/images/Projects/10MHzRefDistAmp/moddedGPSDOFront.jpg)
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Looks cool Masta! By the way, I'm using Lady Heather 5.0 with my BG7TBL GPSDO's and works great. Unfortunately, it won't detect the Datum StarLoc II. I'll have to try to set the thing to look for it. I know reading, if it doesn't detect a receiver, try to give it a boot in the a** . The funny thing is Lady Heather 3.10 did work with it, just not all functions.
Bill
K1FPV
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Unfortunately, it won't detect the Datum StarLoc II. I'll have to try to set the thing to look for it. I know reading, if it doesn't detect a receiver, try to give it a boot in the a** . The funny thing is Lady Heather 3.10 did work with it, just not all functions.
I tried 3.10 with my Starloc II and it does nothing... If the Starloc II sees the packet initialization command that a Thunderbolt expects, it crawls into a corner and sulks and sends nothing. If you have a Starloc II you have to tell Heather that (/rxd command line option) so she can whisper the correct sweet nothings into its ear to get it started. Maybe some firmware difference between my Craploc II and your Craploc II or you were actually connecting to John's internet connected Tbolt?
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Well, I've temporarily put my Starcrap II aside and have been playing with my BG7TBL receiver. With 5.0, I can't seem to get it to display anything but Central Standard Time. I've tried multiple of commands to make it show UTC but no matter what I use, CST is all it displays. :(
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have you told it your time zone is UTC - (or whatever else you want?)
If you are using the Lady Heather program thats in the heather.cfg file
The best documentation for the commands and .cfg file options is in the heather.cpp source.
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So, I have been trying out Lady Heather with two Venus receivers.
Neither have 1PPS currently connected. When I use venus binary mode they both appear to display time one second off and show NO UTC OFFSET permanently. I read something on time-nuts some time ago about a firmware bug. the "leap second upcoming" bug . That is probably what is happening.
Other than that which is likely my hardware, it's an interesting looking program that I hope to make better use of in the future when I have a GPSDO.
The newer of my two receivers is raw data capable and does have the position pinning, elevation mask, etc. settings available and also 1PPS out. (but its USB so not so useful for timing unless its broken out) It does use a TCXO but the kind that just looks like a standard SMT oscillator, and I suspect it manages it itself in its own firmware.
Its very inexpensive considering how good it is.
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When I use venus binary mode they both appear to display time one second off and show NO UTC OFFSET permanently.
Does the screen say "Venus receiver" near the middle of top lines of the screen? Or "NMEA receiver"?
Did you start Heather with the /rxv command? That is needed to get the receiver into Venus binary mode (actually binary mixed with NMEA) unless the receiver has timing firmware (then your firmware sends the $PSTI message that identifies it as a Venus device).
Once Heather identifies the device as a Venus receiver, try writing a log file for a few seconds. WLW command to start, WLS to stop. There will be comments at the start of the log file that have all device/firmware ID info.
After power on, it can take a long time for the UTC offset to come it. The receiver has to download the almanac (15+ minutes) for that to come in.
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Yes, its correctly recognizing both as Venus (Skytraq) receivers correctly.
This is the firmware revision from my s1315F Which is an approximately 2012 Venus 6 also flash based Skytraq chip with raw data output. Very accurate GPS-only- No Glonass or Galileo.
# <name>Venus receiver</name>
# Unit type: Venus GPS receiver
# Kernel: 0001.04.110
# ODM: Ver: 0001.08.23
# Rev: Rev: 0011.05.12
#
#
So, trying a /tsx value of "500" now my ntp-set system clock and the Heather clock display appear to be changing approximately at a similar time but I am still getting the "No UTC OFFSET" alert and the main clock is still displaying in yellow.
Under "operation mode" it says PPS OFF.. and Normal and under that it says "No status avail"
Its tracking 9 satellites or more and the position fix seems accurate enough except that the altitude seems to be truncating the altitude to the nearest meter, also altitude seems off by a significant amount, however the amount keeps changing (?) why - maybe has to do with "geoide" its using?
Quote from: texaspyro on Today at 18:22:01 (https://www.eevblog.com/forum/index.php?topic=51736.msg1092918#msg1092918)
>
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Ok, your Venus 6 probably does not support the timing messages. Heather's code wants a Venus 8 for maximum Venusian goodness. Start Heather with /rxv=17 (/rxv=18 next year) or use the /uo=17 command line option.
You might want to try a Navspark (mini or standard sized one). Mini's are free + $10 shipping or 6 for $36. The standard sized one is around $20. Or maybe Nick Sayer's Venus-8 timing receiver for $40... it's Adafruit pinout compatible. He sells them on Tindie. The Venus-8 timing receivers claim an accuracy of <10 ns. They all need an external antenna with a way to get it to a U.FL connector.
Also try a PE keyboard command and see if that turns PPS on.
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That fixed it!
One cool thing about the Venus receivers is their very fast update rate of 20 hz, so perhaps with 115,200 serial port speed and 20 Hz update the binary messages will be "close enough" - The Venus seems happier (more satellites tracked) with 20 Hz update rate than 1.
Here is what it returns now tsx=48.90 max hits 17 points:592 avg 50.92 sdv: 3.26 ???
Definitely going to get another GPS for timing since they are so cheap, and use it on my Raspberry Pi. Would you recommend the Venus? $40 - I think I would rather use a Navispark to support the project. I already have RTK GPS (but rarely get to play around with it these days) however I do need a precise reliable expandable time source.
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The Venus seems like a decent timing receiver. Timing receivers cost 4-10 times what a normal receiver costs... but are just a firmware change. Ublox sets a one-time programmable fuse at the factory to disable loading timing firmware on a non-timing module (but apparently there are devices out there that can be upgraded to timing devices).
Heather supports changing the update rate on some receivers. The "!n" keyboard command. If the baud rate can't support the data flow funky things can happen. Usually dropped messages, time stamp skips, etc. Also you can get into a condition where processing the serial data doesn't leave any time for Heather to check the keyboard... so no way to set the nav rate back to a lower value. On my system that happens at 20 Hz. If that happens you have to force-quit Heather and use the /nr=1 command line option to go back to 1 Hz without using the keyboard.
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have you told it your time zone is UTC - (or whatever else you want?)
If you are using the Lady Heather program thats in the heather.cfg file
The best documentation for the commands and .cfg file options is in the heather.cpp source.
Yes, I tell it that I want UTC and it still for some reason won't come off of Central time! :(
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Yes, I tell it that I want UTC and it still for some reason won't come off of Central time! :(
Several GPS receivers can be configured to provide the time in either UTC or GPS time. The TG and TU commands tell the receiver to operate on UTC or GPS time. If the receiver can't send GPS times but you use TG (or /tg) to configure the receiver to send GPS time, Heather can adjust receiver time messages to fake them sending GPS time... this requires that Heather knows the GPS-UTC leapsecond offset.
The TZ (or /tz) command tells Heather what time zone or astronomical time scale to display that receiver time in. It takes the receiver provided time and converts it to the time zone that you want displayed.
There are several "special" time zone names that will display the time for that time scale (regardless of whether the receiver is providing UTC or GPS time). Two of those special time zones are "UTC" and "GPS".
To display the clocks in UTC time set the time zone to "UTC" like TZ=UTC or /tz=UTC
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Is Lady Heather rounding off the altitude?
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Is Lady Heather rounding off the altitude?
Nope, Lady Heather is pretty much garbage-in garbage-out. It shows what it gets. Thunderbolts give like 7 decimal digits. Others give it rounded to an integer. No way is 7 digits of precision true...
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texaspyro
Thanks again for such a great program and even more thanks for the Linux support! Glad to see you active here on EEVblog.
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This too is my first post on the forum. I've been following the eevblog saga of the BG7TBL for the last few months with hopes of purchasing one when the infamous "bug" is resolved. I notice Amateurtelecom received a unit with a new data code, 2016-05-31, which was dutifully cataloged in the thread. I've been Google searching this new version for several days on any reference as it relates to the bug. So far nothing has surfaced. If it's fixed, I'll order it. I'm reluctant to query an Ebay reseller as I'm not sure I'd get an accurate answer. If anyone has objective evidence one way or another as to the bugs remediation I, and likely others, would appreciate a post. I realize it may take some time. Thanks again for a new found valuable resource (eevblog that is).
Has anyone been able to confirm this? Thanks all and a really great site!
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I bought mine with this eBayer ( 201377jie ) as he showed a picture of the latest receiver with the 2016-05-31 date on it. I suspect if you buy one with the latest date on it, the seller has them in stock to post the picture in his ad.
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@texaspyro
Please can you post the commandline you use to start LadyHeather? I am to stupid for that or I have connection issues.
(BG7TBL) from 2016
Thank you
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@texaspyro
Please can you post the commandline you use to start LadyHeather? I am to stupid for that or I have connection issues.
(BG7TBL) from 2016
Sorry, but there are soooo many different BG7TBL models out there, I have no idea which one you have. Or what operating system you are running.
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@texaspyro
Please can you post the commandline you use to start LadyHeather? I am to stupid for that or I have connection issues.
(BG7TBL) from 2016
Thank you
« Last Edit: Yesterday at 05:05:28 PM by Fennec »
This is the one I use for Lady Heather in the northeast USA. It works great here with both my BG7TBL GPSDOs. [ "C:\Program Files (x86)\Heather 5.0\heather.exe" /8 /tz=-5EST ]
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I forgot to mention in the last post, the 8 is for my COM 8 which is the Com port I have it on with my Windows 10 machine.
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Hi,
thank you for your help. My TTL adapter seems to be ded. I measure crap only.
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Hello all, Can someone dump the config file for their unit from U-blox U-center. I accidentally hit File -> GGNS and may have wiped it but i'm not sure :palm: . Thanks
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Which U-Blox modul you have? In my bg7bl from mid 2016 is a LEA-7 and I have no clue if it is compatible with other versions.
There is a standard config file in your u-center folder called flash.txt.
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I haven't opened mine up yet so i'm not sure what chip i have exactly but U-center tells me that my product id is 01A7 . I just noticed that it's using the chip oscillator instead of the 10Mhz TXCO. That's why i thought i wiped the config. I will open it up after i get back from work.
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The GPS on my board is the NEO-7M-0-000
The marking on it is 1PPS&10k GPSDO
BG7TBL 2016-05-01
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that looks like it ! thanks !
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Is Lady Heather rounding off the altitude?
Yes, mine is rounded off at 50.000000 Meters in altitude while 2 other programs say 48 & 53 meters in elevation.
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My problem is I've gotten spoiled by another (fun and educational) program (http://gpspp.sakura.ne.jp/indexe.html) that doesnt work with most cheap hardware but does with some, which does all the calculation itself, simply pulling raw data out of the GPS. Basically it uses the GPSs as one would use a giant tape measure. It has accuracy thats better than one meter and so to see it rounded off to the nearest meter was disconcerting to me.. (stupid because most GPSs, even nice timing GPSs are not accurate enough to make it matter beyond one meter, so adding extra digits of phony accuracy is meaningless)
Not that I am actually using this accuracy right now, just dicking around with the hardware and trying to figure out what the best cheap antenna solution is. (The key to it being super accurate is the antenna)
Cheap, high precision GPS is similar to high precision voltage or current or timing measurement, its one of those tools that lends itself to the solving of zillions of problems. Things people otherwise wouldn't think of as possible.
For example, the fact that all the satellites exact positions are known and so even the tiniest movement of the receiver can be determined, means that RTKlib can be used for measuring the exact movement of the land during an earthquake. The differences in RF absorption and reflectance can be used to calculate things about the ground beneath the receiving antenna.. it could be used for automation in agriculture and construction., stuff like that.
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Is Lady Heather rounding off the altitude?
Yes, mine is rounded off at 50.000000 Meters in altitude while 2 other programs say 48 & 53 meters in elevation.
Lady Heather doesn't round off anything. It reports the value that the receiver sends... much to some people's chagrin. If the receiver sends an altitude value with 7 decimal places, that's what gets shown. There's no way a GPS can be that accurate, but if that's what the receiver says, that's what gets shown. If the receiver rounds the altitude to the nearest mile, that's what gets shown.
The number if digits that Heather uses to display the receiver values was chosen to make the lat/lon/alt columns align and look pretty...
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Receive last version (2016-05-31) of BG7TBL on Friday:
http://www.ebay.fr/itm/171742240714?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.fr/itm/171742240714?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
Kind vendor (diyelecmall108), very reactive: ordered on 01-16, received on 01-27.
The device is excellent, GPS lock is fast (a few minutes), even inside my house.
Here is a screen copy of the square wave signal.
Connected to the PC with a RS232-USB interface (be carefull, it is true RS232, with negative voltage). I tried Lady Heather then u-center. At the moment I prefer u-center, as I didn't succeed in displaying something with large enough characters with Lady Heather (even with /vc=1360x768).
Thanks to the antenna fitted with a 5 meters cable, next week I will install the antenna on the roof and will have then a quite professional installation :-)
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I have my gpsdo hooked up to my raspberry pi. Using a GPS antenna from eBay. It's working great. I still have to get my level shifter working to get the extended details in Lady Heather. I also use the same raspberry pi for my data logger and graphing.
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I got a new RF generator recently and in testing it and checking its internal oscillator, I may have stumbled on an issue with the BG7TBL GPSDO that I've got... I believe it's the most recent version, but I've posted it earlier in this thread (now there's BNC holes through the date on the PCB front panel ;) )
Anyways, I was using a Fluke PM6690 (12 digits/s 100ps resolution counter with 1s gate time) with a high stability reference (not the highest stability option, but two up from base model TCXO) and my new HP E4431B ESG-D generator, also with the high stability internal reference option. I had the generator going straight into the option C input on the counter and a 1GHz -20dB signal turned on.
With the external reference for both, the timing noise is quite low (both instruments are pretty high spec), amounting to 3x10^-12 peak to peak frequency variation over almost 2000 seconds of recording time:
(http://www.medpants.com/gpsdo%20test/allgpsdo.jpg)
(http://www.medpants.com/gpsdo%20test/allgpsdodata.jpg)
So using the shared external reference, there is very little variation in either the generation or counting of signals - a sanity check for the quality of the system.
Then with each instrument using their own internal oscillators, you see a predicted fluctuation due to the oven operation, up to 0.7Hz (7x10^-11) peak to peak:
(http://www.medpants.com/gpsdo%20test/internalosc.jpg)
(http://www.medpants.com/gpsdo%20test/internaloscdata.jpg)
But when you assign one instrument to the external GPSDO reference and one to its own (and this goes for either instrument), while the performance is still slightly better than the internal oscillators... there's a very strange step behavior from the GPSDO timing signal, which is clear and obviously visible. It's also not characteristic of the response of regular drift in a frequency standard - it looks almost like it's the visible steps of the DAC being used to drive the OCXO's adjustment voltage (for reference, the fine adjustment of the HP E4431B's oscillator has a step size of 1/2 to 1/3 of this, somewhere between 100 and 150 mHz at 1GHz generated).
First with the counter locked to the GPSDO:
(http://www.medpants.com/gpsdo%20test/countergpsdo.jpg)
(http://www.medpants.com/gpsdo%20test/countergpsdodata.jpg)
Then with the generator locked to the GPSDO:
(http://www.medpants.com/gpsdo%20test/gengpsdo.jpg)
(http://www.medpants.com/gpsdo%20test/gengpsdodata.jpg)
Some really odd looking behavior... and given that the spec was advertised with a least significant digit ballpark of 10^-12.... I don't have real confidence that it's getting there, at least in the current configuration. The GPS was locked to 8+ satellites the whole time (verified through the serial port), and while either instrument with the GPSDO referenced to the other had better performance than just the internal oscillators.... it really wasn't by much.... and if you figure that the runtime for the two instrument oscillators on their own was twice as long, they may actually have had better short term stability than the GPSDO's oscillator. While the GPSDO should still have either one bested in terms of long-term drift, I was a bit disappointed in the short term timing and the strange frequency artifacts i measured in this test.
Probably still worth the $140 or so it cost, but I had higher hopes for it than what this suggests.
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Well, I guess the reason for buying it and how it is used can mean much more to some folks than others. I bought mine initially as a backup to my HP-58503A. I use the 10 MHz reference with my B&K Precision 1823A 2.4 GHz counter. I use this combo periodically to check the frequency readout of my various pieces of equipment. When reading the frequency of TCXO's on various rigs, if the TCXO is 99.999999 MHz or less, I can get an accurate reading down to 1/10th of a Hertz. When I switch from the HP reference to the BG7TBL reference, I usually see no difference. I've since acquired a Spectracom GPS Ageless Master Oscillator, and it too sees no difference.
For what I am using it for as I'm sure most amateurs who periodically use it for working on radios to check frequency, it is a decent reference. If more accuracy is needed, then I'm sure other more costly GPS references would be needed especially if the frequency measurements were well above 1 GHz and needing a clean output. But for most typical amateur radio use, this reference is a good buy for the $$$.
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i suspect the oscilloquartz and trimble based bg7tbl units don't have these artifacts.
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Hi Folks, I just recently picked up a Zyfer 380-210 GPSDO for a heck of a good price. I hooked it up and it locked on the the GPS sats relatively quick and when checking the accuracy of the 10 MHz output, it was dead on according to my setup which measures down to .01 Hz. My question is what software monitors or controls this GPSDO? Lady Heather 5.0 won't even recognize it and I've tried several other programs without success.
Anyone have any suggestions?
Bill
K1FPV
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Receive last version (2016-05-31) of BG7TBL on Friday:
http://www.ebay.fr/itm/171742240714?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.fr/itm/171742240714?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
It is not the latest Version. My Board (2016-5-1, same layout and OCXO) includes a newer Ublox NEO-7M-0-000. Your's is a much older NEO 6, if the pictures are correct.
Lady Heather 5.0 won't even recognize it and I've tried several other programs without success.
Anyone have any suggestions?
Did you check the protocoll with a terminal programm like hyperterm minicom or something like that ?
Check out which protocoll this thing use, thats the first you have to do.
Then you can try U-Center witzh the ublox or NMEA protocoll. Some NMEA runs with the Thunderbolt Monitor only. http://www.prc68.com/I/ThunderBolt.shtml (http://www.prc68.com/I/ThunderBolt.shtml)
The Ublox wouldnt work with the Thunderbolt Monitor.
Maybe you post a few pix, which kind of GPS receiver is included ?
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Does the frequency offset issue still exist with the latest version BG7TBL units? Has anyone tried slurping the firmware off to see where the issue is?
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Yes to all the have you tried xxxxx ! Lady Heather is oblivious to the receiver as is SatStat, U-Center, GPS-Con, PUTTY, Termite 3.3 & GPS View! I've had the receiver running for quite a few hours and it is rock stable on 10 MHz. I'd just love to be able to see what is going on internally and/or control the receiver.
I got the typical excuse from Zyfer that it is obsolete and no longer supported. I'll bet if I could look, they would still have the software for this receiver someplace. The actual name Zyfer gave it is the NanoSync, model 380-210, rev. H. Too bad....it is a cute and compact unit.
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Did you find the manuals for it? According to the User's Manual and RS-232 Programming Manual, it should respond to any terminal program.
Ed
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Ya, this picture says nothing.
You have to find RXD, TXD and GND.
Follow the traces from the UART connector and find the chip. Sometimes it is a simple rs232 converter/level shifter, sometimes they goes direct to the controller. Try find the Datasheet.
With a scope it is easy to find the UART lines at the connector pins.
You have connect them to a TTL - USB converter, NOT direct to the RS232 from the PC, because it is a TTL Signal. Rx -to Tx and Tx to Rx. GND to GND. With some probing you can easy find the data in a terminal program.
Most times it is 9600,8,N,1 and you should see anything. If you see nothing, you have a wrong hardware wiring. If you see crap, play with the settings.
Maybe someone with better english can help you.
Take it apart and make better pictures, so maybe we can help you than.
For sure you have a trimble chipset if it helps...
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contact trimble and see if you can get documentation for the board. oscilloquartz was kind enough to provide us with documentation for their gpsdo.
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contact trimble and see if you can get documentation for the board.
To find two simple datalines ? Sry, but a lill overkilled, don't you think ?!
oscilloquartz was kind enough to provide us with documentation for their gpsdo.
Which information you got ? A few pictures or more ?
Did you got the source-code for the AVR, because an U-Blox M8 wouldn't work in this unit. Downgrade to a U-Blox 6M is also not possible. I don't know why.
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oscilloquartz was kind enough to provide us with documentation for their gpsdo.
Which information you got ? A few pictures or more ?
Did you got the source-code for the AVR, because an U-Blox M8 wouldn't work in this unit. Downgrade to a U-Blox 6M is also not possible. I don't know why.
see this post (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg740339/#msg740339). you did read the whole thread, didn't you? ;D
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contact trimble and see if you can get documentation for the board. oscilloquartz was kind enough to provide us with documentation for their gpsdo.
Trimble doesn't know anything about it. FEI-Zyfer took a Trimble GPS receiver and put it into their GPSDO. Only the FEI-Zyfer manuals will help K1FPV. Luckily, the Wayback Machine has copies of those documents.
Ed
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see this post (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg740339/#msg740339). you did read the whole thread, didn't you? ;D
I am not sure what you want to tell me with your post. Your Link has nothing, but really nothing to do with the bg7tbl.
Does anyone tested the U-Blox M8 in this Unit without the US-GPS?
China and russian GPS works fine, but it wouldn't lock. I think there is a different data string between the U-Blox M7 and M8 that the AVR not "understand". I'll check it later, if I have any idea how I can put the complete U-Blox board onto the BG7TBL withount desolder all the chips.
Also I have to find a way to "pinning" the Ovens. I think I have 5 or more different Oven here and I wanna test them in this device.
Ideas are welcome.
My Unit is the latest one 5/31/2016 but with the newer U-Blox neo M7
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Yes to all the have you tried xxxxx ! Lady Heather is oblivious to the receiver as is SatStat, U-Center, GPS-Con, PUTTY, Termite 3.3 & GPS View! I've had the receiver running for quite a few hours and it is rock stable on 10 MHz. I'd just love to be able to see what is going on internally and/or control the receiver.
the trimble documentation for this gps receiver:
Serial ports/1PPS: CMOS TTL levels
Supported Protocols: TSIP @ 9600 baud, 8-Odd-1 (confi gurable)
TAIP @ 4800 baud, 8-None-1 (confi gurable)
NMEA 0183 v2.1 @ 4800 baud, 8-None-1 (confi gurable)
RTCM SC-104 @ 4800 baud, 8-None-1
NMEA messages: GGA, VTG, GLL, ZDA, GSV, GSA and RMC
messages selectable by TSIP command; selection
stored in non-volatile memory
you will need to probe the 8-pin header on the left of the trimble board for RS232 access direct to the gps.
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the zyfer unit appears to be using a morion OCXO. given zyfer's relationship with morion, this seems likely.
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I got the typical excuse from Zyfer that it is obsolete and no longer supported. I'll bet if I could look, they would still have the software for this receiver someplace. The actual name Zyfer gave it is the NanoSync, model 380-210, rev. H. Too bad....it is a cute and compact unit.
here you go. page 2-3 shows the pinout. you should be able to hack a connector up and see if lady heather can talk to the trimble.
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Quick question to the experts on this thread:
just got a Trimble 57963-D board. I get the 1PPS pulses OK and the 10MHz signal once it has done the self-survey at the proper connectors.
All fine up to date from the hardware point of view. LED behaviour is also as expected.
Using Lady-Heather with the RS-232 J5 contacts, it finds it OK and seem to be working BUT for one thing. It only seems to update every two seconds.
Then I used the Teraterm terminal emulator to talk to the unit but it does seem to be outputting the time and other data every two seconds all by itself (not on request) thus messing up the communications.
It looks like the unit is programmed to output the time data every two seconds. That messes up communications. Is there an easy way to set up the board to go in request mode and only output that data when asked?
Cheers and thanks.
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The next version of Heather has code to fake the missing odd seconds. Version 5.0 fakes them internally, but the faked seconds happen so fast they don't usually show up on the screen.
If you are using a Linux build, I can send you the latest source code to build. Most people can't build the Windows version and most email systems block sending .EXE files.
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Exactly what I am seeing. Thanks for the quick reply and the nice software (if I understand correctly you are the author?) texaspyro.
Any though if it is possible to reconfigure the Trimble board itself to stop that behaviour since Lady Heather can send commands to it?
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trimble documentation says you can change the NMEA auto reporting frequency with TSIP command 0x7A. see pages 3-4 and A-50.
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Exactly what I am seeing. Thanks for the quick reply and the nice software (if I understand correctly you are the author?) texaspyro.
Any though if it is possible to reconfigure the Trimble board itself to stop that behaviour since Lady Heather can send commands to it?
Yep, I wrote it.
If you send the receiver the command "TOD DI" will disable the time code message and "TOD EN" will enable it. Heather depends upon it being enabled for proper operation.
If you are running Heather and talking to the receiver, the "!t" keyboard command will enter terminal emulator mode. You can issue commands to the receiver. the END key will exit terminal emulator mode... this might cause Heather to re-initialize the receiver and the time code message. You can also send a user command to the receiver with the "!u" keyboard command. Without the time code message, Heather will detect a loss of serial port data and try to re-initialize communications to the device.
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Exactly what I am seeing. Thanks for the quick reply and the nice software (if I understand correctly you are the author?) texaspyro.
Any though if it is possible to reconfigure the Trimble board itself to stop that behaviour since Lady Heather can send commands to it?
If you send the receiver the command "TOD DI" will disable the time code message and "TOD EN" will enable it. Heather depends upon it being enabled for proper operation.
Did that and it works well. Thanks. I also tried some of the command listed when doing a "help" or "?" request.
BTW: also noted that the command OUT:TP:SEL? does not work but if you try OUTP:TP:SEL? it does work.Same thing with its PP1S sister OUTP....
Wonder if this typo is on my unit model only or might be more generalised to the whole 57963-D series....
I was not able to change to RS-232 output to 1PPS however, just the hardware pulse.
Been too busy to spend much time on this but glad that Lady Heather indicates that the unit is stable and reliable.
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Thanks for the info usagi. I managed to find the information in the "Trimble Standard Interface Protocol" on the web and slowly going through the whole thing.
Just been too busy to make much progress these past few days.
So I use the "" 0x10, id, data, 0x10 0x03 "" command format and the sub header if required. Something like 10 7A 00 10 03 and send it to the RS232 port.
Only get a bad header or bad command response. Tried several formats but obviously doing something wrong here or the port is configured with the wrong protocol.
If you look at my previous post I can talk to the unit OK using the commands (not all) listed by "help" request.... so the port works.
More |O required before :-+ obviously.
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These "UCCM" units don't speak TSIP.
Also that "OUT:..." in the help menu is a typo.
Also also, you can't change the 2 second time code message output rate.
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Thanks texaspyro :)
Guess I'll stop going down that path then.... and wait for your next version of Lady Heather.
Any hint why the program is named Lady Heather by the way?
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Any hint why the program is named Lady Heather by the way?
I could tell you, but then she would beat me mercilessly... :box:
Actually it was a combination of three Heather's within a week:
1) I went over to a friend's house and she was watching a movie called "Heathers" on TV.
2) It was near Halloween and a friend and his girlfriend (named Heather) stopped by on their way to a party. She was dressed as a naughty nurse/maid/dungeon queen/something oooh-la-la and had a riding crop.
3) At the time, the TV program CSI had a recurring character named Lady Heather that was a dominatrix. The program was for controlling gps DISCIPLINED oscillators.
'Twas karma that made me do it...
Then there's also the story about some government funded lab that uses it, but before that could do that they had to edit the icon. So the slighly risqué name helps keep any stuck-up riff-raff away.
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Hi,
on my BG7TBL build with an Ublox M7 modul, there was a chemical damaged Backup Capacitor or is it a Battery, idk. So I lost the whole config and the device would'nt lock anymore. I can't find the right setup :-//
Please can anybody help me out and send me the config file for the UCenter software ?
It is pretty easy. Check out >Tools > GNSS Configuration. Hit GNSS > File, save it and post it here or pm me.
Thank you. ;)
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I think the serial port on the BG7TBL GPSDO's is output only and you can't send commands to the Ublox.
One thing to try is to momentarily short circuit the battery with the unit powered down. This should corrupt the config RAM and the Ublox firmware should re-initialize it from flash memory. This has worked on several Ublox and Sirf based modules I have.
If BG7TBL set a custom config in RAM and didn't save it in flash, you are probably screwed. Note that with the Ublox there are two levels of flash storage for the config. The first is a user defined config. The next is the factory defaults which are usually only loaded via a software command. I don't know what happens if the RAM and user flash configs are both corrupted.
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> The next is the factory defaults which are usually only loaded via a software command. I don't know what happens if the RAM and user flash configs are both corrupted.
You likely would need to have access to the appropriate firmware file so you could reflash it.
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You likely would need to have access to the appropriate firmware file so you could reflash it.
If the flash firmware gets corrupted is should revert to the ROM firmware.
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I just ordered one of the newer versions of the BG7TBL with the mod. date of 2017-03-29. I'm curious to see the differences internally. Now if I could only locate a copy of the HP/Symmetricom 58531A software for my HP 58540A GPS RX.
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Now if I could only locate a copy of the HP/Symmetricom 58531A software for my HP 58540A GPS RX.
If I had one, I could get Lady Heather to work with it. It is a bit different than the other Z38xx and HP5xxxx devices, but not that much.
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I think the serial port on the BG7TBL GPSDO's is output only and you can't send commands to the Ublox.
Nope, I can send all comands to the modul. It must, because without TX I can't send a cold/warmstart etc. I also can read and write the config file. The Unit works fine, but I got no lock and without a lock this GPSDO is useless.
I think the Modul doesn't run with the defaults. Thats why they have plant in the AVR. Something is different to the default config and I have no Idea what. That's why I need the configuration file.
I've played arround with the config. Most settings I have no clue what they are good for, but for maybe half an hour the Unit has locked. I directly saved the config into the flash, but it would'nt work anymore.
Come on guys. It's 5min of work to read out the config.
Thank you
I just ordered one of the newer versions of the BG7TBL with the mod. date of 2017-03-29. I'm curious to see the differences internally.
Where you found the teardown pictures? Is there still the ublox M7 inside or the newer M8N.
Btw. does anyone tried to read out the AVR?
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Why don't you look up BG7TBL in a Chinese callbook or see if he has a web site and shoot him an email?
But first try to exhaust your obvious low hanging fruit fixes..
The GPS is likely producing NMEA or a binary data stream. What is it saying? Can you paste the stream into a post here?
Also, are you sure you cleaned the board well, maybe the damaging chemical left some residue on the board which is preventing it from performing as its should, in other words, maybe its still there,
I would remove all batteries, and following the instructions elsewhere here on cleaning off water damaged boards and/or flux residue, clean the board and then dry it thoroughly before re-use.
GPS is high enough frequency that even a small amount of flux residue on an RF board substantially decreases performance.
Maybe some other similar residue is causing the decline. That may be your problem right there.
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Where you found the teardown pictures? Is there still the ublox M7 inside or the newer M8N.
The pictures of the exterior were on the sight that this seller was advertising it on eBay. ( thanksbuyer-hobby (8884 ) There were no pictures of the inside! I asked him before buying it which date was on each of them and he said 2017-03-29 which was pictured. I'll let you know when it comes in.
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Darn, I wish I was able to locate a copy of the HP 58531A comm program for the HP 58540 GPS receiver. I've got a receiver, it is locked exactly on 10.000,00000 as measured with my counter using another GPSDO. Unfortunately, I'm unable to communicate with it. I've used HyperTerminal, PUTTY, and Termite. No luck! >:(
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I think you have a DTR and cable issue.
The Protocoll is SCPI. Factory default 9600 baud, 8 data,1 stop bit, no parity. I am sure it works with a FTDI232BM cable/adapter (ebay 381374421597) because this chip has the full RS232 pin assignment.
I like to use hterm as grafical terminal.
http://www.der-hammer.info/terminal/ (http://www.der-hammer.info/terminal/)
Send *IDN? and I bet you got an answer.
See attached Datasheet.
I'll let you know when it comes in.
Hope you make some pics.
Why don't you look up BG7TBL in a Chinese callbook or see if he has a web site and shoot him an email?
Because they didn't answer and for the most here they have connect his BG7TBL to a PC it is 2min of work to send me a config file.
The GPS is likely producing NMEA or a binary data stream. What is it saying? Can you paste the stream into a post here?
It "says" the standard NMEA protocoll like all of the UBLOX modules I have with the default settings. Nothing special.
Also, are you sure you cleaned the board well, maybe the damaging chemical left some residue on the board which is preventing it from performing as its should, in other words, maybe its still there,
I would remove all batteries, and following the instructions elsewhere here on cleaning off water damaged boards and/or flux residue, clean the board and then dry it thoroughly before re-use.
GPS is high enough frequency that even a small amount of flux residue on an RF board substantially decreases performance.
Maybe some other similar residue is causing the decline. That may be your problem right there.
Ya, the Hardware works fine.
@all
I still need a UCenter config file for the NEO 7M or lower version.
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Darn, I wish I was able to locate a copy of the HP 58531A comm program for the HP 58540 GPS receiver. I've got a receiver, it is locked exactly on 10.000,00000 as measured with my counter using another GPSDO. Unfortunately, I'm unable to communicate with it. I've used HyperTerminal, PUTTY, and Termite. No luck! >:(
A terminal program should work fine with it.
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Send *IDN? and I bet you got an answer.
And try ending the command with LF. Some SCPI devices want the commands to end with CR, others LF, and I have a couple that want CR and LF.
Also, most HP equipment needs a null modem cable to talk to a PC.
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And try ending the command with LF. Some SCPI devices want the commands to end with CR, others LF, and I have a couple that want CR and LF.
Also, most HP equipment needs a null modem cable to talk to a PC.
True. Thats why I like to use hterm for SCPI communications. You also can set commands in a timer. For example to request your frequency every 10s or something like that.
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Have you tried searching on Github to see if somebody has written a Linux version of Ucenter or similar.. sometimes 3rd party apps, especially on Linux are more useful for understanding how devices communicate than the manufacturers apps.
Also, try running the windows equivalent of strings (whatever that is) on the binary maybe you'll get some clues in the revealed error messages.
Also, why not ask questions more specifically about whatever is going wrong. "cannot get 3D fix" You also should post some of the NEMA messages you are getting (since no 3D fix its not going to give your location away)
Did you try communicating with it with GPSD, for example?
Also, and from experience, this is more often than not the problem, whatever USB-UART device you're using, if its not working, swap it out for another one. Just try that.
Another idea, when you bring it up you may need to tell it roughly where you are and what day month year etc it is. Normally it saves some of that info.. The older the GPS the less sensitive it is, so you also need a GOOD SIGNAL for at least 13 minutes minimum to get the ephemeris. Any interruption at all, it has to keep trying. Sometimes if a GPS has been sitting in a drawer for a while you would swear it was dead and then suddenly, poof, its alive.
Use a decent amplified antenna and put it outside, not just on your windowsill.
Another idea, try putting some ferrite split beads on the USB-UART.. or other devices youre using.. why not.. maybe its causing RFI at 1.575 GHz you have no idea.. GPS signals are pretty weak....
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Have you tried searching on Github to see if somebody has written a Linux version of Ucenter or similar..
Lady Heather will work with it (and just about any GPS receiver or GPSDO, including GPSD). It should auto-detect NMEA and Ublox devices.
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Also, why not ask questions more specifically about whatever is going wrong.
I did. I wrote "the hardware works fine, GPS too, but no lock."
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Was a firmware update ever released for the BG7TBL to fix the minor error?
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Thanks, I'd like to know too. I was considering the 2017 model. (note that I'm not really familiar with this topic, but am interested in GPSDO)
Is it confirmed that the star4 and trimble versions do not have bug and can be controlled by Lady Heather? I read no versions can be and that there is no actual oscillator disciplining
(earlier in this thread by usagi)
http://www.ebay.com/itm/10Mhz-GPSDO-OSCILLOQUARTZ-OSA-OEM-GPS-GPSDO-10MHz-1PPS-STAR-GPS-Clock-/262861459973 (http://www.ebay.com/itm/10Mhz-GPSDO-OSCILLOQUARTZ-OSA-OEM-GPS-GPSDO-10MHz-1PPS-STAR-GPS-Clock-/262861459973)
There is a version with both sine and square 10M outputs, maybe not a bg7tbl variant.
http://www.ebay.com/itm/Trimble-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-sine-and-square-wave/252162780444 (http://www.ebay.com/itm/Trimble-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-sine-and-square-wave/252162780444)
Otherwise, would it be better to consider just the trimble or NEC module (no control interface?) or a trimble thunderbolt?
I forgot to put in the mix the Low Jitter Precision GPSDO Reference Oscillator if I just wanted a reference.
Thanks.
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Otherwise, would it be better to consider just the trimble or NEC module (no control interface?) or a trimble thunderbolt?
The latest version (5.01 or later) of Lady Heather works will with the Star-4 and NEC GPSDOs. It must be connected to the "management interface" serial port... which is a logic level interface, you will need a level shifter to use it with RS-232 serial ports.
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The only units that had the frequency error are the ones where he built his own circuit from scratch. Any of the units that include another GPSDO (Trimble, Symmetricom, Oscilloquartz) were fine. I've heard that his later units fixed the frequency error, but I've never seen any test results.
Ed
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Thanks, I broke down and bought a variant of the bg7btl with a Trimble 57963 with the 73090 OCXO (I read these were updated versions of the ThunderBolt?). This one has the additional square wave output. Date code in the ebay pic anyway is 0953.? Are these serial ports really RS232 levels or 5V TTL? I recall seeing one with a USB-TTL plugged right into the top row of the connector. Maybe he was using some kind of max chip?
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Thanks, I broke down and bought a ....
:clap:
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Otherwise, would it be better to consider just the trimble or NEC module (no control interface?) or a trimble thunderbolt?
The latest version (5.01 or later) of Lady Heather works will with the Star-4 and NEC GPSDOs. It must be connected to the "management interface" serial port... which is a logic level interface, you will need a level shifter to use it with RS-232 serial ports.
The seller of the star-4 has reworked the interface so it will work with Lady Heather. There are screenshots of it in the auction. I wish I had the newer unit that has that change.
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The seller of the star-4 has reworked the interface so it will work with Lady Heather. There are screenshots of it in the auction. I wish I had the newer unit that has that change.
You can modify the device. There are two pins (needles) that connect the Star-4 GPS receiver RXD and TXD to his interface board (I think that some builds used pogo pins and others may have soldered the connections). Remove the pins to break the connection to the GPS receiver and wire the pads to the GPS management interface TXD and RXD on the Star-4 connector. His connection to the Star-4 connector has vias for most or all of the Star-4 connections.
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Have you tried searching on Github to see if somebody has written a Linux version of Ucenter or similar..
Lady Heather will work with it (and just about any GPS receiver or GPSDO, including GPSD). It should auto-detect NMEA and Ublox devices.
I have an Arbiter GPSDO 1083A similar to this: http://www.arbiter.com/catalog/product/model-1083b.php (http://www.arbiter.com/catalog/product/model-1083b.php) that an older version of Lady Heather didn't talk to. It seems they have their own command set etc. but its fully documented. I got it because it has a Wenzel 5 MHz streamline oscillator and a Motorola receiver. I figured I could screw around for ages and not get better results. I can supply docs if interested. I also have a Tbolt that works great with LH.
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Bought latest version of the BG7TBL.
My first freq reference. 8)
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BG7TBL 2017-03-29 teardown
OCXO: CTS 970-2178-46
GPS: u-blox NEO-7M-0-000
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Nice
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Nope! Can't get any of the 3 terminal programs to work with it. I've already tried Termite 3.2, PUTTY as well as HyperTerminal. I'll just have to see if I can locate someone with HP/Symmetricom 58531A and use that program.
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Nope! Can't get any of the 3 terminal programs to work with it. I've already tried Termite 3.2, PUTTY as well as HyperTerminal. I'll just have to see if I can locate someone with HP/Symmetricom 58531A and use that program.
Somebody may have changed the default baud rate settings. It can run at 1200, 2400, 9600, or 19200 baud. even/odd/no parity, 7 or 8 data bits, 1 or 2 stop bits. Also they had an option that changed the serial port from DTE or DCE mode.
I would try the various baud rate settings by sending the "*IDN?" command. Try ending the command with a <CR>. If no response, try with a <LF>. If you get no response at that baud rate try with the different data bit settings. If parity is wrong, I think it sends an error code prompt. If all that fails, try with a null modem cable.
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@1GHz
Thank you for the Pics. On a first look I see nothing differnet to my older version from 5/2016. What I see are the ovens goes cheaper and cheaper I think. I didn't take a deeper look into the datascheets between mine and yours.
@all
My Unit is fixed now. A big thanks to all of the forum members who didn't help me out with this easy copy of the GNSS File which I really needed :--
- I desoldered the UBlox Module and plant it directly into the case in my active antenna on the roof. Because my cable is over 100ft long and the Unit can handle active antennas 3 or 5V.
- I plant in two cheap class1 Bluetooth modules to transfer the Data to the Unit and read them out. Not really the best Idea, I think I change them to WIFI. So I can place the Device directly close the Counter, Generator and so on.
- I changed the cheap ass Oven to a Morion 89A (its a Double Oven) Used, but they are good quality ones for this price. $US60 (ebay)
Maybe I put a filter into the output, but I am not shure. Let's see, I am waiting for the parts.
Nope! Can't get any of the 3 terminal programs to work with it. I've already tried Termite 3.2, PUTTY as well as HyperTerminal. I'll just have to see if I can locate someone with HP/Symmetricom 58531A and use that program.
Did you read my last post? Don't think so :palm:
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Nope! Can't get any of the 3 terminal programs to work with it. I've already tried Termite 3.2, PUTTY as well as HyperTerminal. I'll just have to see if I can locate someone with HP/Symmetricom 58531A and use that program.
I assume it is the one I sold as the 58540a isn't very common. It is 9600/8/n/1 100% for certain. I only used a terminal program with it(putty in my case), never did locate the HP Software.
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@all
My Unit is fixed now. A big thanks to all of the forum members who didn't help me out with this easy copy of the GNSS File which I really needed :--
With such a petty and childish post, I for one won't be helping you with anything should I have the opportunity. Expecting everyone to jump to help you on your command is a sure way to get ignored. Perhaps an apology might be in order for being an ass to those who help for free.
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With such a petty and childish post, I for one won't be helping you with anything should I have the opportunity. Expecting everyone to jump to help you on your command is a sure way to get ignored. Perhaps an apology might be in order for being an ass to those who help for free.
look at his post history.
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A forum Member sent me the GNSS file via PM now. Thank you very much!
It is possible to read out the AVR. It's an ATmega8L on my BG7TBL 5/31/2016
See attached files. Maybe someone would rebuild it with an Arduino and UBLOX shield. Should be easy.
If you want to use the UBLOX M8N which can receive US-GPS, GLONASS, Beidou you have to change the Antenna to a dual one! Use an active one. With this setting I reveive over 20 SAT fixes !
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Its interesting how he now seems to be able to to use cheaper non-timing GPS's to discipline his hardware OCXOs.
BG7TBL has been able to push the envelope pretty far as what can be done with cheap GPS hardware.
Generally, the larger and therefore less highly optimized ceramic patch antennas are more broadband than the smaller ones.
You can make your own asymmetrical patch antenna (RHCP) using air as the dielectric.
It will be larger than the ceramic, maybe twice as large but much more likely to work ~25 MHz higher. (GLONASS)
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Its interesting how he now seems to be able to to use cheaper non-timing GPS's to discipline his hardware OCXOs.
BG7TBL has been able to push the envelope pretty far as what can be done with cheap GPS hardware.
As long as a GPS receiver puts out some kind of signal, usually 1 PPS, you can use it to discipline an OCXO. The question is what kind of performance will you see? The long term frequency error for any properly designed GPS receiver will be zero, regardless of what type it is. The differences, if any, should show up in short-term measurements.
For a navigation receiver, the 1 PPS output is something of a minor afterthought so it gets low priority. On some older navigation receivers, I've seen the 1 PPS accuracy specified in the microsecond range.
On a timing receiver, the 1 PPS output is the main output while the location is sort of a minor afterthought. The code is optimized to provide the lowest possible error on the timing output(s). I've posted numbers in the past that showed the period of the 1 PPS output with a Standard Deviation of a few nanoseconds and a maximum range of 50 nanoseconds or less.
TBH, I've never seen a direct comparison of the output of a GPSDO built with a navigation receiver vs. a timing receiver. It might be possible to adjust the PLL parameters for the nav-based GPSDO to minimize the short-term differences.
Ed
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With GPS being used in phones and UAVs and such now, the line has been substantially blurred. There are still navigation receivers that advertise 100ns or more jitter on their PPS output, but there are receivers marketed for location tracking or other non-timing uses that can do better than +-50ns jitter.
The very best timing receiver specifications I've seen are 15ns RMS on one datasheet and +-20ns on another. Not sure which of those would actually be the better performer, I think you'd have to do some long term comparisons (and I actually have such an experiment planned with a couple of receivers) to figure out how the specs compare.
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non-bg7tbl gpsdo discussion:
My GPSDO came in. It is not BG7TBL, but similar with the Trimble module. http://www.ebay.com/itm/Trimble-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-sine-and-square-wave-/252162780444 (http://www.ebay.com/itm/Trimble-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-sine-and-square-wave-/252162780444)
There is 2Vpp sine with 2V DC offset. The 10M square and PPS look fine. It's stable so far and my 5314A has not moved (0.1) in an hour, reads 3.9 Hz high.
I have a solid ACT led, but do not understand the RS232 output. I just poked my probe into the RX connector and it looks similar to: https://core-electronics.com.au/media/wysiwyg/rigol/ultra-scope-screenshot.png (https://core-electronics.com.au/media/wysiwyg/rigol/ultra-scope-screenshot.png)
Except the negative pulse arrives first and there is ~20us offset between the negative pulse and positive pulse. I get ~8ms pulse train like that every 2 seconds. Level is -5V to +5V. I'm trying to use Rigol DS1054Z to decode it with several baud rates. :-//
I thought RS232 had like 12V and should look like regular serial data anyway (inverted)?
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Some Trimble receivers, like the Thunderbolt, have some firmware issue where they may fail to start with the right date after yesterday.
>My GPSDO came in. It is not BG7TBL, but similar with the Trimble module...
Just guessing that one can probably compensate for it in software if its basic functionality remains unchanged.
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Either your probe isn't making a good connection in the socket or there's a bad connection further in. The picture you linked to shows the result of looking at a square wave with a very small capacitor in series. You'd see that with a bad connection such as a cracked solder joint. You should see a square wave with limits of something like +-5V to +-10V. Use your scope probe to trace the signal back towards the Trimble board.
Ed
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non-bg7tbl gpsdo discussion:
Some Trimble receivers, like the Thunderbolt, have some firmware issue where they may fail to start with the right date after yesterday.
>My GPSDO came in. It is not BG7TBL, but similar with the Trimble module...
Just guessing that one can probably compensate for it in software if its basic functionality remains unchanged.
Maybe I should not post in this thread because it is not BG7TBL module? I'm not sure what there is to compensate for at this point?
I don't know what it's doing with the LEDs or what state it's in; these are the LED's in sequence:
1. Amber LED is either solid or blinking.
2. Red LED is off, blinks fast, or blinks slow.
3. Red LED always blinks with PPS.
4. Green LED is always on when powered.
When I first powered up, the 1 amber LED blinked slow and then went solid. After a while it started blinking fast.
After longer, the 2 red LED started blinking. It did not look good so I hit the reset (button).
I don't recall the sequences, but I've had various combinations of the first two LEDs blinking fast or slow together, or with the first amber solid. According to the sellers notes:
1. ACT when working,it will flash when gps locking.
2.second one ,it will only flash ONCE when it start to working
3.1pps led.when led flash.1pps will output
> --------------
> aboved all linked from gps board that inside the box(NOT FROM THE RS232 BOARD,DIRECT CONNET TO TRIMBLE GPS BOARD)
> -----------
> 4.DC ,,,it DC working state.Apply power on it..(i made this power module fit the box and gps board)
> ------------
> mact IS BACK to factory reseting
> reset is restart.
I don't know what is actually locked, but once the amber LED was blinking fast, the red LED blinked for a few minutes, then stopped. That might mean it's locked, with a fast blinking LED seems odd though. I removed the GPS antenna and nothing changes, not in any of the states.
Edit:
Pressing MACT seems to swap amber to solid and red blinking, or amber blinking and red off.
It looks like an OCXO to me with some funny pulses out of the RS232 port. I'll ask the seller what he thinks, I'm out of thinking power.
Edit2:
Seller asks me to connect to LadyHeather. Maybe just for grins I will connect the serial line since it's 5V. Not sure if the negative 5 volts will hurt the serial-usb converter. I was also thinking that the first positive impulse could be the start of a bit and the negative pulse intended to be the end of the bit(s). Maybe some interface circuit is required?
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Some older GPSs in GPSDOs need a GPS antenna to draw more current than most current active GPS antennas (only a very few ma) draw to not sound an alarm that the antenna is gone (when it isnt) They might want to see an older style timing antenna which likely draws a bit more current.
The GPSDOS designed for cell site use have an alarm when the GPS antenna is seen as disconnected. They likely expect a certain range of current to be drawn, a bit like a burglar alarm's bell circuit.
If the low current drain in a newer antenna was the problem, you might be able to get them to work by switching to the kind of antenna they normally use (a timing antenna) or somehow modifying the one you have so that slightly more current was drawn by whatever was plugged in as the antenna, but not too much current, which would make it think there was a short.
Have never been in this situation, and don't own a GPSDO yet either, just read about this problem recently.
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non-bg7tbl gpsdo discussion:
Shouldn't the serial data still come out looking like serial data? Also, what would the baud rate be for this trimble module (probably not known, but seller says MACT is back to factory, but I thought that is to force the 10M/PPS outputs?)
Is this trimble unit an upgrade to the thunderbolt or just some unknown variant? I think TheSteve had done some tests on various receivers and he listed something like a Trimble ~UCC~ that had very good PPS stability. I wondered if this is that particular module?
I'm tempted to buy a loose module of the same here to play with. I'd rather get something that actually works though. There is also the NEC modules. I'm starting to get a headache though... |O
Now I'm getting solid amber led with flashing red led. I think that means some kind of error. I'll look up the antenna specs he listed.
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what kind of antenna are you using?
The UART lines for the GPS are often where the information is exchanged between GPS and other components, they may have as many as three or four bidirectional communication channels which may use different formats.. multiple UARTs, USB, SPI, i2c. Look up the manufacturers documentation.
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GPS antenna current is monitored on some units, and with the very few, there's an external IF converter and you actually see a frequency over the DC bias of the antenna connector. Passive GPS antennas almost don't exist to my knowledge - the cable run would need to be so well shielded to let that tiny signal actually make it to the unit it's just not practical. I've seen antennas not specify requiring any sort of power, but every one of them has had an LNA inside that requires a DC bias.
As for the Trimble unit, default baud is usually 9600 or 4800, and there's a chance it uses the TSIP standard to communicate which is not ascii characters but is raw bytes, often with slightly different communication settings (Been working with a Trimble Resolution SMT that uses normal 8 bits one stop, but uses an odd parity bit). Often modules will also have an NMEA 0183 standard output mode, but it may not be the default. I'd try TrimbleStudio or Lady Heather to try and talk to it if you are at least seeing activity on the output - but if it's just the waveform you showed, you're not going to get data from that. edpalmer42's post a couple back may help with getting data out through this line - sounds like a likely board defect.
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Did you miss my reply a few messages back?
You've got a bad connection on the RS-232 output. Find it!
As for the baud rate, you've already measured it! I'm not sure how to read your Rigol screen, but look at the shortest time between the pulses. That's the baud rate. Invert it to go from sec./bit to bits/sec. Take the closest standard bit rate.
If your Rigol is showing 20 us/div, 4 bit times is ~70 us, so 1 bit ~17.5 us. Invert that and you get 57142 bits/sec. So the closest standard rate is 57600 bps. Done.
Yes, from the photo, that appears to be the UCCM GPSDO that was discussed in another message thread. I'm not sure which thread, they're starting to breed like rabbits! ::)
Ed
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:-+ 57600 bps is the default/proper baud rate for a UCCM receiver. Mine is still rocking along.
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Some of my GPS receivers work well enough with a passive antenna, even indoors, to make it possible to just use one.
The signals are stronger with an active antenna.
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non-bg7tbl gpsdo discussion:
what kind of antenna are you using?
The UART lines for the GPS are often where the information is exchanged between GPS and other components, they may have as many as three or four bidirectional communication channels which may use different formats.. multiple UARTs, USB, SPI, i2c. Look up the manufacturers documentation.
I'm using a small 3-5V patch antenna, 28dB gain.
Did you miss my reply a few messages back?
You've got a bad connection on the RS-232 output. Find it!
As for the baud rate, you've already measured it! I'm not sure how to read your Rigol screen, but look at the shortest time between the pulses. That's the baud rate. Invert it to go from sec./bit to bits/sec. Take the closest standard bit rate.
If your Rigol is showing 20 us/div, 4 bit times is ~70 us, so 1 bit ~17.5 us. Invert that and you get 57142 bits/sec. So the closest standard rate is 57600 bps. Done.
Yes, from the photo, that appears to be the UCCM GPSDO that was discussed in another message thread. I'm not sure which thread, they're starting to breed like rabbits! ::)
Ed
I did not miss the post, but was hoping the seller would notice my scope capture. How would I just connect this to LH anyway? Do the negative pulses need to be inverted, and then correct the pulse width or does that not matter (I know you said there is connection issue and can sort that out after exhausting things with seller)? Would I need to use a max232 chip to convert it to TTL? I'm using a CH340G with my Lassen LP GPS module and that works fine with LH after I use Trimble studio to set the comm to NMEA (the default TSIP does not communicate with LH, and NMEA does not communicate with Trimble studio). I think -5V pulses to my serial converter will not work.
I also have a laptop with LH with an actual serial port, but then I don't know if real RS232 to the GPSDO unit will blow up the Trimble module or something else in there, I mean it has the 1PPS pulse on that comm port.
Thanks for the help folks.
BTW, I hit the MACT button before I left it today and that made the amber LED blink. There is 4.8V on the antenna center. I can measure the current into the antenna, there are a couple more of the Chinese puck antennas on order, I think I'm using a name brand puck.
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What does "MACT" stand for?
Did you find anything useful searching for stuff on uccm gpsdo ?
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non-bg7tbl gpsdo discussion:
No idea, exactly. The term appears often on Time Nuts mailer and on this forum in other threads about GPSDO's
The seller says it goes to factory default, other thread here seemed to indicate if forces output of 1pps and 10MHz, which are apparently normally off until the unit is locked. Maybe it is Manual ACT. No idea what ACT means either as that is another term/label on an LED. Maybe for active or activity?
Google gives sparse results or results that do not seem to apply.
Edit: it's also silkscreened onto the Trimble board, top of board (not my board): https://photos.google.com/share/AF1QipMrbcX7Cs9tz8OXElph4wmw7cN98hqN2SXsafAtCgdJD9KTgU1do9q7CIfz5tkJ2g?key=ZXdIYmNHaWFjVVF5eVg2eERISGtONk03eXJFR1RR (https://photos.google.com/share/AF1QipMrbcX7Cs9tz8OXElph4wmw7cN98hqN2SXsafAtCgdJD9KTgU1do9q7CIfz5tkJ2g?key=ZXdIYmNHaWFjVVF5eVg2eERISGtONk03eXJFR1RR)
Also, how can I find this guy's post who describes the communication in detail?
https://www.febo.com/pipermail/time-nuts/2015-September/093893.html (https://www.febo.com/pipermail/time-nuts/2015-September/093893.html)
Think I found it:
https://www.febo.com/pipermail/time-nuts/2015-August/093612.html (https://www.febo.com/pipermail/time-nuts/2015-August/093612.html)
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You definitely don't want it putting out a PPS or frequency reference until it can be sure its accurate.
Here is another GPSDO thread, this one is from last year.
https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-%28ocxo-furuno-receiver%29/650/ (https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-%28ocxo-furuno-receiver%29/650/)
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I did not miss the post, but was hoping the seller would notice my scope capture. How would I just connect this to LH anyway?
I don't know how the guy wired up the box, but on the board there is a place for a 4 pin header that has the 56k baud serial port at RS-232 levels. This should be what is connected to the DB-9 connector (DE-9 if you want to get pedantic). I don't have the pinouts handy, but there are posts on the forum that show what they are.
The signals you are seeing indicate a bad connection somewhere.
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Here's the signal on J5, pin 2 of my Trimble UCCM board. ~+-5V @ 57600 bps. This is the first two characters in the 'UCCM>' prompt - actually, it's carriage return, linefeed. If your signal isn't somewhat similar, the fault is in the Trimble board, rather than anything on the BG7TBL interface board. Does he process the signal at all, or just pass it to the RS-232 connector?
With GPS lock, the green led is flashing quickly. That's the green led on the bottom of the Trimble board. I don't know how that relates to the LEDs on the panel.
Ed
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non-bg7tbl gpsdo discussion:
Looks like I'll have some reading to do, but first the hard part, finding my screwdriver :box:
BTW, it immediately put out PPS and 10M on first power-up. I wanted to see how the signals came up.
Thanks guys!
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Does it have a 50 connection header?
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non-bg7tbl gpsdo discussion:
Never mind this rest of this post. I found a different pin with the same signal as I found earlier on the RS232 port. Maybe it just needs a max232 chip to interface with it. :-//
I cannot tell if it ever locks. I get solid ACT with blinking on the other LED. Maybe that is locked. I'm going to go read the other thread.
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He has nicely made boards in there. There is a ribbon header and interface cable going to another board. The daughter board ribbon header also has an unpopulated DIP header that I probed and found good TTL signal. The trace goes to a glass diode D1 - signal good one side, spike on the other. The diode does not looked cracked, but there is something like a bubble inside, not round, just like a 3/4 filled bottle of liquid kind of line. I diode check one way .7V, the other 1.7V (I get similar readings on a scrap board with similar diodes - measured in circuit). The diode goes to pin 17 of 74ACT244.
Also, I tried all the baud rates. First decode happened at 115200 (I had polarity negative here). :-// Higher rates gave more characters, but nothing particular good.
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https://www.ti.com/lit/ds/symlink/max3232.pdf (https://www.ti.com/lit/ds/symlink/max3232.pdf)
will give you more UARTS
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non-bg7tbl gpsdo discussion:
I wired up a max233 this morning and it just squared off the very short impulses, I guess what one would expect, and it does not communicate of course.
It could be the ribbon cable not making good contact, but then I'm perplexed with the earlier circuit/result I posted above, why the other UART going through a diode changes a square data pulse to a very short impulse with decay when it just feeds a buffer? :-//
I also noticed by studying my PCB image above and his PCB image on the ebay ad that mine is missing an IC, the right side between the buffers (I think those are both buffers). That might not be needed, so I need to probus the Trimble and see if the ribbon connection is the problem (the Trimble unit looks nice and clean with clear coat of something - it should work!).
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probably non-bg7tbl gpsdo discussions would be better in a separate thread...
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probably non-bg7tbl gpsdo discussions would be better in a separate thread...
My apologies, I mentioned that earlier...I'll fix what I can.
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The seller of the star-4 has reworked the interface so it will work with Lady Heather. There are screenshots of it in the auction. I wish I had the newer unit that has that change.
You can modify the device. There are two pins (needles) that connect the Star-4 GPS receiver RXD and TXD to his interface board (I think that some builds used pogo pins and others may have soldered the connections). Remove the pins to break the connection to the GPS receiver and wire the pads to the GPS management interface TXD and RXD on the Star-4 connector. His connection to the Star-4 connector has vias for most or all of the Star-4 connections.
I managed to get the Star-4 working in Management mode. I cut the two pins which went to the bottom board. Then wires from the Managements vias to the two pins spot. Worked great.
Thanks for the help.
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The Star-4 GPSDO also has a connection on the board for the 10mhz square wave. It pretty crusty though.
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You have a 50 ohm input on the scope? It could be just that the high impedance and the cable inductance is making it overshoot a bit.
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You have a 50 ohm input on the scope? It could be just that the high impedance and the cable inductance is making it overshoot a bit.
Yep.... I throw my 50ohm on it and do another screenshot. Thanks for jogging my memory. The Star-4 with the ubox LEA-5T and OSCILLOQUARTZ 8663 double oven is a great unit. Winner Winner chicken dinner.
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Yep.... I throw my 50ohm on it and do another screenshot. Thanks for jogging my memory. The Star-4 with the ubox LEA-5T and OSCILLOQUARTZ 8663 double oven is a great unit. Winner Winner chicken dinner.
No problem, I think there's a post of mine in this thread when I first got it with the same issue :-DD
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I wonder if I can upgrade the inbox GPS from a ubox LEA-5T to the LEA-8MT. The datasheet says it's backwards compatible. It would be a nice upgrade.
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I wonder if I can upgrade the inbox GPS from a ubox LEA-5T to the LEA-8MT. The datasheet says it's backwards compatible. It would be a nice upgrade.
Yes you can, but you have to config the new Module and upgrade the Antenna.
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I wonder if I can upgrade the inbox GPS from a ubox LEA-5T to the LEA-8MT. The datasheet says it's backwards compatible. It would be a nice upgrade.
Yes you can, but you have to config the new Module and upgrade the Antenna.
Ok.. It's not worth the trouble then.
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A raw M8T module is also like 1/2 of the price of the GPSDO - currently the cheaper M8T is $89 in single quantities...
To my knowledge, the M8T's timing specification is no better than the 6T, not sure how that compares to the 5T, but there was no 7T and the current generation BG7TBL gpsdos seem to use the M7 series modules, which are not specifically designed for timing.
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I finally added a top BNC connector to the STAR-4 for the 10mhz square wave output. I terminated into 50 ohms. Here is the screenshot. Better looking.
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A little update on mine:
I've upgraded time references to a custom job based on an SRS PRS10 rubidium module and a Trimble Resolution SMT GPS receiver, so I figured I would try to properly measure the BG7TBL GPSDO that I've got, and the preliminary results (only 1.5 days of warm up/stabilization on the rubidium) are quite a bit better than the ones I made with high stability internal oscillators in instruments before. So without further ado...
Using the BG7TBL GPSDO 2016-05-31 which uses the Ublox Neo M7 GPS module and a Bliley OCXO, about 40k seconds worth of recording, 1 second gate time, 100ps resolution counter
(http://medpants.com/pics/bg7tblgpsdo/bg7tbl%20prelim%20graph.jpg)
(http://medpants.com/pics/bg7tblgpsdo/bg7tbl%20prelim%20stats.jpg)
The rubidium oscillator should be at least an order of magnitude better in terms of stability, and the timing rating on the Resolution SMT is roughly 4-5x better than the Neo M8's, so the reference primarily in the noise of the measurement, though I will repeat the test with a full week of stabilization to be sure.
You still see a little of the coarse adjustment step behavior, but they happen much less frequently - don't know if this is antenna position related or just that it's been on for a long time (the BG7TBL has been on for weeks), but it's not jumping around like I had measured earlier, just infrequent adjustments to stay where it should be. Looks like performance is pretty solid, and the minimum adjustment steps running into the VCO are about 1.5mHz in width. There have been some ambient temperature swings over the duration of the test, but I don't see a huge correlation - I think most of the smaller curves are the heating cycle of the oven or something, hard to say because while you get NEMA output, you don't get much info on what the CPLD is doing.
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Try the Venus timing receiver (available from Navspark and (for quite a bit less) Nick Sayer on Tindie). They are quite a bit better than the Res-T (about 1/3 the sawtooth error in the 1PPS).
Also, rubidiums are generally more stable than OCXOs, they tend to be quite a bit more noisy. In a GPSDO you are usually better off with an OCXO. The GPS will keep it on freq so the low drift of a rubidium doesn't bring much to the table except for better holdover if you lose GPS (which for a modern GPS receiver takes a REALLY crappy antenna setup).
And remember Mark's Rule of Rubidiums... the smaller they are, the crappier they are. The UCT-8663 DOCXO (at the time, 10 for $100) that I put in my HP-53132A counter is around twice as good as my Symmetricom X72's (both drift and particularly noise wise).
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Well at least in the case of the PRS10, the module is a rubidium disciplined OCXO with a self contained pps disciplining circuit, so it was really easy to build into something and should do a good job of things (and the spec sheet confirms that).
Hadn't heard of the Venus, though, I'd be interested in getting my hands on one at some point. I've got a few GPS receivers with a PPS output and once the Rb reference is fully stabilized, I want to try to measure their jitter - datasheets seem to be pretty inconsistent in methods of reporting it if they mention it at all. I think the Neo M7 is something like +-80ns, but the Resolution SMT is 15ns RMS (no peak numbers), and the Neo 8T is +-20ns, same as the LEA 6T. Got a few to play around with, but seeing if I can pick up a jupiter 31 or a LEA 5T to toss into the testing mix, since they seem to be fairly commonly available.
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seeing if I can pick up a jupiter 31 or a LEA 5T to toss into the testing mix, since they seem to be fairly commonly available.
My Venus receivers report a sawtooth error of +/- 6.1 ns.
I'm currently using a LEA 5T (with an indoor antenna) to test some new code in Lady Heather that disciplines a Symmetricom X72/X99/SA22.c I'm using an indoor antenna to help get a noisy 1PPS. The LEA 5T board has two outputs programmed for 1PPS. One is quite a bit noisier than the other. I'm seeing typical 1PPS jitter of around +/- 16-67 ns (the Symmetricom time interval counter has a resolution of 16.667 ns).
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I connected a Tbolt to the 1PPS input of a Symmetricom SA22.c rubidium oscillator and ran Heather's software discipling code on it. For some strange reason, you do get better performance using a clean 1PPS rather than the crappiest one you can find ;-)
Anyway some interesting results came out. White traces are the DDS frequency offset Heather is using to steer the SA22.c output freq, yellow are temperature, magenta is the difference between the 1PPS in and 1PPS out (16.666 ns res of the SA22.c TIC). The TIC reading is used to steer the rubidium's DDS output frequency.
The straight white and yellow traces are linear regression trend lines of those parameters. A little math shows a clear dependence of the SA22 output freq on temperature of around 2.664E-11 parts per degree C.
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Still a day off of full stabilization of the Rb reference and a good measurement, but I found something interesting. I had been letting the counter go during the day to try to get a sense of how the Rb stabilized over time, and I realized yesterday that I was getting a pretty good correlation with changes of temperature in the room, so after some consideration, I put the BG7TBL module in a fancy thermal isolation chamber (soft sided lunchbox) to isolate it somewhat from the thermal changes of the room. It improves stability a lot! You still get the digital adjustments of frequency, but it improves the variation in between those steps by quite a bit, easily 2-4x. Since the chassis is just aluminum and it's only a single oven, a temperature change in the room or moving air near it does make the frequency drift - it will still be close, but extra insulation dramatically reduces that drift.
Also interesting, picking up the reference and putting it in a soft sided lunchbox (and changing its orientation somewhat) makes a pretty big shift in frequency because of physical orientation, like as much as one Hertz difference, and it takes some hours for the reference to settle down and reconfigure itself. I started seeing a good flat response (like pictured) around 12 hours after it spent a few minutes at an angle and then was moved to be level again.
I've also noticed that at least relative to the rubidium source, the BG7TBL is consistently just a tiny bit fast. Typically around 1.5-1.8 millihertz, but it's rare to see the long term average (looking at about 12-16h blocks of data) much lower than that and in 6 days of measuring, I haven't seen it low.
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Still a day off of full stabilization of the Rb reference and a good measurement, but I found something interesting. I had been letting the counter go during the day to try to get a sense of how the Rb stabilized over time, and I realized yesterday that I was getting a pretty good correlation with changes of temperature in the room, so after some consideration, I put the BG7TBL module in a fancy thermal isolation chamber (soft sided lunchbox) to isolate it somewhat from the thermal changes of the room. It improves stability a lot! You still get the digital adjustments of frequency, but it improves the variation in between those steps by quite a bit, easily 2-4x. Since the chassis is just aluminum and it's only a single oven, a temperature change in the room or moving air near it does make the frequency drift - it will still be close, but extra insulation dramatically reduces that drift.
I've heard people say that a cardboard box is useful to isolate a unit from drafts and other thermal effects. Other than that, you're looking at something like active temperature control or using lots of mass to provide thermal 'inertia'.
Also interesting, picking up the reference and putting it in a soft sided lunchbox (and changing its orientation somewhat) makes a pretty big shift in frequency because of physical orientation, like as much as one Hertz difference, and it takes some hours for the reference to settle down and reconfigure itself. I started seeing a good flat response (like pictured) around 12 hours after it spent a few minutes at an angle and then was moved to be level again.
Are you talking about tilting the GPSDO or turning it left or right? If tilting, OCXOs are sensitive to gravity. Dave did a video on it a while back. Turning a GPSDO left or right shouldn't have an effect, but it might make a difference to a Rb standard since it uses magnetism to set the frequency. The case is usually made of Mu metal to reduce the effect.
I've also noticed that at least relative to the rubidium source, the BG7TBL is consistently just a tiny bit fast. Typically around 1.5-1.8 millihertz, but it's rare to see the long term average (looking at about 12-16h blocks of data) much lower than that and in 6 days of measuring, I haven't seen it low.
Not good. That's always been the problem with the BG7TBL units that he built from scratch. I thought he'd fixed that. Can you test it against another GPSDO? Ideally, measure the time interval between the two PPS signals and capture the data on a computer using something like Timelab. If there's any consistent drift over a period of a day or two, your unit has the problem. Keep in mind that 'problem' is a relative term. The frequency difference is negligible for anyone other than a Time Nut!
Ed
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The Rb source being measured is my other GPSDO and it's almost to a week's worth of settling time, I expect to be doing a little analysis of PPS timings though, as the datasheets even for timing receivers don't seem to give a lot of detail in terms of what your actually going to see in terms of PPS timing jitter. I've got this ublox M7, the Resolution SMT in the Rb GPSDO, then a ublox M8T, a ublox 6M, and I'm trying to get a hold of another one or two to test (maybe Motorola M12/M12+, Jupiter 31, or ublox 5T?) just to get a sort of apples-to-apples test of the PPS accuracy instead of trying to compare +-XXns to XXns RMS and whatnot.
Yes it was tilting it up to get it into the lunchbox while still powered up... I just hadn't realized what was going on until after a few minutes of gawking at the spike, neat to see the physical nature of the oscillation in action, though.
As for the measurement, I don't have a TimePod, so the most accurate timing info I can get is with my PM6690, and I don't know if that will interface with TimeLab. The intention was to use the Rb GPSDO as the reference clock and then measure interval lengths, but with two inputs I can measure time difference between two PPS pulses against each other too. When I get some fully stabilized data for this I'll post previous day's plots and statistics, I've been capturing data pretty much all this week using the Rb GPSDO as the frequency reference and the BG7TBL as the input and the 1.5ish microhertz has been consistent over long intervals (I'm getting 40-50k seconds per measurement, generally).
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Here are some measurements I've made on various GPS receivers and GPSDOs.
GPS Devices -- Measure & analyze the period of the 1 PPS Output
Device ............... Std Dev (ns).... Range (max-min)(ns) ... Device ...... Notes
Navsync CW12 ......... 4 - 5 .......... 20 - 25 ............... GPS Rcvr .... 1,7
Motorola UT+ ......... 40 - 55 ........ 95 - 110 .............. GPS Rcvr .... 2,7
Rockwell Jupiter ..... 10 ............ 50 ................... GPS Rcvr .... 3,7
Motorola M12M ........ 10 - 15 ........ 40 - 60 ............... GPS Rcvr .... 7
Trimble Thunderbolt .. 0.4 - 0.5 ...... 2 - 4 ................. GPSDO ....... 6,8
HP Z3801A ............ 0.1 - 0.2 ...... < 1 ................... GPSDO ....... 6
HP Z3817A / CW12 ..... < 0.1 .......... < 1 ................... GPSDO ....... 4,6
Jackson Labs GPSTCXO . 0.3 - 0.4 ...... 2 - 3 ................. GPSDO ....... 6
NEC NWM-034241-201 ... 0.1 - 0.2 ...... < 2 ................... GPSDO ....... 5
Trimble UCCM ......... 0.09 - 0.11 .... < 1 ................... GPSDO ....... 5
Results are based on multiple runs of ~ 1000 measurements each.
Sawtooth correction has not been used for any of the GPS receivers. Where supported, it would reduce the numbers substantially.
All units were connected to the same antenna system.
Notes
1. Sawtooth correction not supported.
2. Most 'range' results were in this group, but there were a few at 20 - 30.
3. Only one test.
4. Requires external 1 PPS input. Equipped with E1938 oscillator.
5. Measurement made with Fluke PM6681.
6. Measurement made with HP 5370B.
7. Measurement made with HP 5372A.
8. Standard parameters.
9. Optimized parameters. (Not yet used in any tests)
Normally, Std. Dev. shouldn't be used with quartz oscillators because frequency drift messes up the calculations. However, in a GPSDO there is no drift so, AFAIK, it's okay.
If Timelab supports your counter, you should be able to duplicate these results.
Ed
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I'll definitely look into it then. I've seen it around and it seems to be standard - this counter is a rebrand of a counter sold under several major manufacturers, so I suspect it is then. Will be nice to get something automated to extract the data too, the display info is great, but it's a real pain to try and recover all the data points and look in detail from a lot of measurements.
Looks like some impressive numbers on the outputs of the GPSDOs too.
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As for the measurement, I don't have a TimePod, so the most accurate timing info I can get is with my PM6690, and I don't know if that will interface with TimeLab.
You might want to look into the TAPR TICC. Two channels, 60 ps resolution. It works with Timelab or Lady Heather. Timelab can handle live ASCII data streams from a device or file. Also data from a logged file. If Timelab can't handle your counter's native data format log it to a file and convert it to a format it can handle. You can do this either post-processed or in real time. Heather can configure and control the TAPR TICC.
Lady Heather now supports counters as an input device. It can handle input data as frequency, interval, period, or timestamps. Internally, it converts all readings to time interval errors (the difference between the nominal frequency and the measured frequency converted to seconds).
Heather can calculate ADEV, HDEV, MDEV, TDEV, MTIE, frequency, phase, etc on up to four channels of data with two TAPR TICCs or two channels with generic counters. Heather always shows frequency as the difference between the nominal frequency and the measured frequency.
If your counter can shovel data out a serial port (or a USB port that looks like a serial port) it should work. It wants ASCII data at, ideally, 1 Hz gate time (but should be able to handle at least 10 Hz). The numeric parser is rather general purpose and can handle the HP531xx data format.
Attached is a screen dump of Heather monitoring a SA22.c rubidium oscillator using a TAPR TICC which is using an HP5071A cesium beam oscillator as its reference clock. It shows the SA22's temperature dependence. The SA22 baseplate temperature changed 1.25 degrees C during that run. You can see the air conditioning cycling and where it shut off.
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It just occurred to me that you might not need Timelab to duplicate my results. I have a PM6681 counter from Fluke/Philips/Pendulum. I can set it up to take 1000 measurements of the 1 PPS period and give me Min, Max, and Std. Dev. No computer required. I would expect your counter to have those capabilities.
Ed
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A while back I think I saw software to use a Venus GPS and a Raspberry Pi to timestamp events - Its on "dan.drown.org" I think.. Probably his githib.
Wonder if a way could be finagled to make the whole more accurate than the sum of the parts? Possibly with a GPSDO and the RPIs GPIOs??
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A little update on my testing:
I've taken 4 or 5 segments of 50k second samples in different conditions after more than a week of continuous operation. In my tests I found conclusive evidence of thermal drift in the BG7TBL, but in trying to figure out what it's coming from (the ublox 7M does not use a TCXO, there is a regular crystal on the board as well, and then there's always the potential for drift in the VCO adjustment supply), I found that the GPS was unlocking, sometimes for quite some time, and not reporting errors... so I can't count those results as an accurate representation of the unit's actual performance.
Before I jump to any hasty conclusions.... I've moved to a higher gain antenna and will let the thing resettle and repeat the tests. I can still see clear drift in the PPS output due to no temperature compensation in the GPS module oscillator, but I can also see the jumps vary in frequency to try and stay centered around the correct frequency. I did not get enough data captured to see where it fully settled before an unlock in yesterday's tests, so I'll be looking into that too.
The tests I did before included putting the BG7TBL unit in a lunchbox, then also thermally isolating the rubidium source to make sure it wasn't the source of the variation (and in later tests I confirmed that at least within the temperatures I was looking at, it was quite stable). I did see the average frequency elevated when it was keeping itself warm in the lunchbox and by cracking open the back lid just a tad (2mm vent on the short side), I was able to finally get a 50ks average frequency just under 10MHz.... but since there's the possibility that the GPS was unlocked at that time, I don't think they're results you can count on.
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The GPS module oscillator has very little effect on the GPSDO freq. The GPSDO slaves to the GPS 1PPS output which is derived from a combination of the GPS module oscillator and the GPS signal. The difference is known as the sawtooth correction and is typically in the range of +/- 10-50 ns. The GPSDO takes care of averaging out the sawtooth error and steering the OCXO to 10 MHz.
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Can basically confirm that today, first half of the capture is enclosed and 4-5C above ambient outside the case, second half is in open air. While you can see the drift, you can also see the pwm-style adjustment happening, and it's been pretty right on the nose in terms of frequency - less than 1e-10 every time I checked, half that after almost 10k seconds recording.
Also looks like for the Neo 7M, the adjustment step for the PPS output is about 10ns.
So if there's still drift from temperature, it's not from the GPS module. Hopefully the next two days will be an open air 12-14h test, then a similar test that's half covered (elevated temp) and half not to see if there's still some change in the 10MHz output.
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Well I've got good news. The drift in my initial results seems to be entirely because of the unlocking GPS. The unit is not without its quirks, but it's certainly disciplining to the right frequency, not a high one. This was taken with about 3 days of continuous GPS lock/uptime:
(http://medpants.com/pics/bg7tblgpsdo/bg7tbl%20stability.jpg)
(http://medpants.com/pics/bg7tblgpsdo/bg7tbl%20stability%20stats.jpg)
You can see variation, but the unit always compensates for it properly and converges to 10MHz (I actually caught 10.000 000 000 000 several times when watching the samples accrue). Just after 11ks in, I actually took off a bubble wrap bag that had been insulating the unit and keeping it about 5C above normal temperature since the night before, and the result is hardly notable in the noise and was fairly quickly compensated for.
As I mentioned though, it's not entirely without its faults. I had missed the fact that the GPS was unlocked earlier because the normal on behavior, a PPS pulse, is not actually from the GPS, it's from the micro inside. Even though there's a PPS light on the board internally that is only on when locked, the blinking light on the outside goes all the time, and the GPS lock is instead indicated by a second, solid green light.
Another, much more relevant, issue is the way it adjusts. The adjustment step size is fairly large, while I said 1.5mHz before, it's probably closer to 1.6mHz after seeing some more, and another 2-3 bits worth of adjustment on the DAC could make it MUCH smoother. The adjustment algorithm is also fairly quick to respond to changes in the PPS input, and the PPS output from the neo 7M is somewhat noisy, also with its large step adjustment size. The algorithm also seems to have no minimum time between step transitions, and is happy enough to jump two steps at once.... which really seems too aggressive for a reference designed to take hours to settle and stabilize. I took a picture of the graph at a much shorter sample length that demonstrates these fairly quick transitions, and I haven't seen the frequency of adjustments decrease with more uptime. Even with the same DAC, I think limiting the adjustment to one step at a time and perhaps one minute or so in between steps should go a long way towards reducing the frantic variation of the current system. Maybe not a huge improvement, but a free one.
(http://medpants.com/pics/bg7tblgpsdo/bg7tbl%20adjustments.jpg)
Performance is still good, though, especially given the price. This 2016-05-31 model seems to have fixed any long term frequency drift issues and is disciplining to the correct place.
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I've been using my BG7TGBL GPDSO (version 2017-03-29) as a reference for a project but one thing that throws a wrench in the works is that the 1PPS output wanders around a lot (20ns) compared to the 10MHz output.
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Been running my GPSDO (non bg7tbl) Star4+ Oscilloquartz unit for a few days now. Very happy indeed. External 26dB ebay timing antenna on 8m of LMR400 cable. This all via RS232 to USB with PPS signal to Lady Heather. See attached.
I have as yet no means to measure Allen Variance. As this is a hobby only, what would be the easiest and/or cheapest way to do so? TICC? I do need to get a Counter still, only counter is the Siglent one in my SigGen and my (new to me) OScope Tek TDS2014 with FFT :-DD Best I can do under my budget, no SA for me. So for a counter I am considering a HP 53131A together with possibly a TICC.
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Hmmmm,
I've noticed that with Heather 3.10, the program reads out to the exact U.T.C time right to the second. In the meantime, Heather 5.0 is off by 17 seconds. Anyone else notice that?
Bill,
K1FPV
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I've noticed that with Heather 3.10, the program reads out to the exact U.T.C time right to the second. In the meantime, Heather 5.0 is off by 17 seconds. Anyone else notice that?
Which GPS receiver does it use? I think BGLTBL has more versions than birthdays...
The 17 second offset is due to the receiver being in GPS time and Heather in UTC time (or the other way around). Try the TG and TU keyboard commands.
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OK....that did it! Now everything is on the same time!
Thanks,
Bill
K1FPV
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Has anyone here used this GPSDO with a built in LCD Screen? It sells for $209 on Ebay. Listed as - GPSDO-Symmetricom Inside, 10 MHz GPSDO, with Power Supply, Antenna, and Display.
Example: http://www.ebay.com/itm/GPSDO-Symmetricom-Inside-GPS-10MHz-1PPS-GPS-Disciplined-Clock-GPS-Ant-Display-/172166437092?hash=item2815eb58e4:g:Ze8AAOSw1DtXFbR8 (http://www.ebay.com/itm/GPSDO-Symmetricom-Inside-GPS-10MHz-1PPS-GPS-Disciplined-Clock-GPS-Ant-Display-/172166437092?hash=item2815eb58e4:g:Ze8AAOSw1DtXFbR8)
It looks interesting with the Display.
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When using Lady Heather's '/rxu' switch with the BG7TBL '3-29-2017,' the 'run' LED stops flashing (either turns off or steady-on, depending on state when command issued), and fewer satellites are displayed as 'green.' More information is displayed, like the firmware revision and additional observations, but the reduced number of active satellites is weird. A subsequent "/rxn" returns the 'RUN' LED to flashing, and the dropped satellites turn 'green.' Is this normal? This unit uses the NEO-7M receiver. Anyone else see this?
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Hi,
Please excuse the newbie type questions but I could use some helpful pointers here.
I've had the 2015-09-17 version of the BG7TBL unit (with an NEO-6M unit inside) for quite some time but only just now thought I'd have a play with the RS232 port on it to see what it can do. Problem is I can't seem to have it output anything what so ever.
I've scoped the TX-pin and it just sits idle high all the time, nothing's comming out. I've connected it to a PC and lanched Lady Heather which scans for modules but comes up empty. I've tried terminal program at various baudrate - nothing. Tried sending your typical characters like cr, lf, etc but it seems to not do anything what so ever. It is happily outputting the 10MHz and 1pps signals.
Questions:
1) What should come out the serial port of the unit? (I thought it was NMEA strings at 4800 baud)
2) Do I need to do some circuit surgury in order to get it talking to Lady Heather?
3) Did a new firmware version with a fix for the small frequency error ever surface?
Thanks and, once again, I appologize for the newbie question, I've browsed this thread for quite some time without arriving at any definitive answers.
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Hi,
Please excuse the newbie type questions but I could use some helpful pointers here.
I've had the 2015-09-17 version of the BG7TBL unit (with an NEO-6M unit inside) for quite some time but only just now thought I'd have a play with the RS232 port on it to see what it can do. Problem is I can't seem to have it output anything what so ever.
The BG7TBL GPSDO can't be controlled via software that I know of, but you can read and use its received data in the following software.
Compatible Software: Freeware: VisualGPSView, http://www.visualgps.net (http://www.visualgps.net) This software is great and should make you happy enough.
Note: Some USB/RS-232 Adapters, etc, require opening the RTS {7} and CTS {8} lines & connecting them together on the PC side. A DIY 9 Pin F to M adapter can be fabricated for this function.
EDIT: I don't think 'Lady Heather' will work with the BG7TBL GPSDO, but I know that 'VisualGPSView' I suggested above will. You just may very well need to modify your RS-232 connections as I described.
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You can use a GPSDO's 1PPS as a super accurate, low jitter source of timing data by using one of he flow control lines in the RS232 connection to connect it to your computer via the serial port.
The NMEA data is no more accurate than a net time server, but a 1PPS from a good GPSDO if it is locked to UTC time is likely to measurably better than the 1PPS from a GPS alone in terms of jitter.
Don't use USB for this, if you can avoid it, as it impacts accuracy a lot..
An RS-232 level PPS signal should be on the DCD line
Make sure you get the polarity right.. If you are using NTP and one of NTPs refclocks, read the documentation closely, there are a lot of settings which can tell your computer which edge of the signal and which signal to use as the beginning of the second.
Getting that "fudge factor" right is likely to heavily impact the accuracy of your setup.
A GPSDO is one of the most accurate, lowest jitter sources of timing data available. But all that accuracy is wasted as far as NTP goes by attempting to use it with a USB serial port.
The more bare metal the interrupt is, the better.
This is from David Taylor's web site on setting up NTP- This page is one of a great many on his site on NTP setup and accuracy. Its about a specific GPS but it contains a lot of useful info on serial port setups.
http://www.satsignal.eu/ntp/Sure-GPS.htm#pps (http://www.satsignal.eu/ntp/Sure-GPS.htm#pps)
Krysztof Zaraska notes:
USB-TTL converters (I'm using FT232) use "assert low" logic, meaning that low DCD is seen as asserted. Your site mentions this, but you don't say that if the PPS signal is directly hooked to the DCD pin of FT232, this results in NTP detecting the PPS source, but showing that the PPS source is off by 100ms (as it is looking at the wrong edge of the PPS pulse). Seeing this behaviour can be... confusing.
You recommend using a CMOS inverter to flip the pulse polarity. I have found that at least with the GPS receiver I am using (Neo-6M from ublox) there is a simpler way: there is manufacturer's application (u-center) which allows you to set PPS pulse polarity.
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You can use a GPSDO's 1PPS as a super accurate, low jitter source of timing data by using one of he flow control lines in the RS232 connection to connect it to your computer via the serial port.
The NMEA data is no more accurate than a net time server, but a 1PPS from a good GPSDO if it is locked to UTC time is likely to measurably better than the 1PPS from a GPS alone in terms of jitter.
That depends on what timescale you are looking. The 1PPS output of the BG7TBL drifts around 50ns compared to the 10MHz output so I wouldn't call it low jitter.
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You can use a GPSDO's 1PPS as a super accurate, low jitter source of timing data by using one of he flow control lines in the RS232 connection to connect it to your computer via the serial port.
The NMEA data is no more accurate than a net time server, but a 1PPS from a good GPSDO if it is locked to UTC time is likely to measurably better than the 1PPS from a GPS alone in terms of jitter.
That depends on what timescale you are looking. The 1PPS output of the BG7TBL drifts around 50ns compared to the 10MHz output so I wouldn't call it low jitter.
This. I've actually been measuring a number of PPS outputs from GPS units and they are not particularly stable - they have a relatively coarse adjustment step and basically switch over the center in intervals proportional to how far away they currently are. If you took a hardware counter that counted to 10 million and used the 10MHz reference out as the clock for it, you would get a nice, stable PPS output, but the BG7TBL unit (at least the one I have) just outputs the PPS signal directly from the GPS, so you don't get the smoothing of the disciplined oscillator.
As for talking to the unit, I would check the internal connections/solder joints, as other posters have run into comm problems related to that. The RS232 on the unit in question should just be the TX/RX from the ublox module directly, so it would be a NMEA output signal, and you should be able to breakout the pins directly from the GPS module if you want to verify that there is data coming from the module.
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That's not good.
Are you sure/
the bg7tbl devices simply pass their internal GPS's pps to their 1pps output?
(without improving it?)
So, people are buying it simply for the 10 MHz and not caring about the time being no more accurate than it is on a GPS? (arguably less accurate because of the apparent inability to set the cable delay, etc.)
Admittedly, the difference is such a small amount its challenging to measure it but still.
If you pay >$100 for a GPSDO but only get half the benefit you might get if it was designed properly, that's not good.
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I don't think 'Lady Heather' will work with the BG7TBL GPSDO, but I know that 'VisualGPSView' I suggested above will. You just may very well need to modify your RS-232 connections as I described.
Heather will work with most GPS receivers including NMEA and Ublox. You might not be able to control the GPSDO features, but if it brings out the receiver serial data Heather should display it. A few GPS receivers power up "mute" and don't send any data until commanded. Heather cannot auto-detect these and you need to specify the receiver type (with the /rx? command) and the GPS serial input line needs to be available.
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Well I don't know 100% if it does not pass through another chip, but the PPS output on my unit (with a Neo 7M) matches the behavior and performance of a Neo M8T and a Neo 7N.... an odd find given the price and the timing specification differences, but it seems like the PPS signal adjustment step is decent sized on all of them, so while the modules are constantly correcting to make the average PPS output be in the right place, the second to second variation is still somewhat noisy. Maybe as part of my tests I'll hook up a couple of 12 bit counters to the output and see how smoothed it actually is, it's slow going because everything needs time to be warmed up and stabilized and then the sample size is around 14h, but I'll have results eventually.
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I'm probably misunderstanding you.
Well I don't know 100% if it does not pass through another chip, but the PPS output on my unit (with a Neo 7M) matches the behavior and performance of a Neo M8T and a Neo 7N.... an odd find given the price and the timing specification differences, but it seems like the PPS signal adjustment step is decent sized on all of them, so while the modules are constantly correcting to make the average PPS output be in the right place, the second to second variation is still somewhat noisy. Maybe as part of my tests I'll hook up a couple of 12 bit counters to the output and see how smoothed it actually is, it's slow going because everything needs time to be warmed up and stabilized and then the sample size is around 14h, but I'll have results eventually.
.... Similarly to how errors show up on the tracks from multiple anything, lets say planes in the same area at the same time, similar timing errors will likely occur on multiple GPSs.. and cancel out.
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Right, my point is that while they converge to exactly one second intervals as they should, the minimum adjustment step for timing a single second is fairly coarse, and it will bounce around between adjustment bits so that averaged over a long period, it's stable, but in the short term, it is not very finely smoothed. If the adjustment step was smaller, the variation from the intended center point could be much smaller. I'm measuring around +-25ns from an exact one second signal total variation, but the minimum adjustment step is around 20ns, so that individual short term measurements based off just the PPS signal could vary considerably, this has been the case across the ublox modules I've measured so far.
If that signal was disciplining an OCXO with a long integration time, then you used the OCXO's output to create another PPS signal, that one could be considerably more stable, probably an order of magnitude or two more than the 2x10^-8 worth of minimum adjustment variation I can see on the module's PPS output. I think this is probably around as good as you can get from a commercial GPS signal without additional smoothing, but the hardware needed to smooth it further is probably already in the box.
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The BG7TBL GPSDO can't be controlled via software that I know of, but you can read and use its received data in the following software.
Compatible Software: Freeware: VisualGPSView, http://www.visualgps.net (http://www.visualgps.net) This software is great and should make you happy enough.
Note: Some USB/RS-232 Adapters, etc, require opening the RTS {7} and CTS {8} lines & connecting them together on the PC side. A DIY 9 Pin F to M adapter can be fabricated for this function.
EDIT: I don't think 'Lady Heather' will work with the BG7TBL GPSDO, but I know that 'VisualGPSView' I suggested above will. You just may very well need to modify your RS-232 connections as I described.
Heather will work with most GPS receivers including NMEA and Ublox. You might not be able to control the GPSDO features, but if it brings out the receiver serial data Heather should display it. A few GPS receivers power up "mute" and don't send any data until commanded. Heather cannot auto-detect these and you need to specify the receiver type (with the /rx? command) and the GPS serial input line needs to be available.
Thank you both. I probed around a bit more today and found that I do have NMEA data at 9600 baud going into the MAX3232 chip in the BG7TBL module but nothing's coming out, I'm reading stange voltages on the V+ and V- pins so something's up with the RS232 tranceiver chip for sure. Tapping off the 3.3V level signal into an FTDI chip gets me data into the PC and Lady Heather displays it without doing anything in particular to it.
I'll see if I have a replacement tranceiver chip.
Thanks again!
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That's not good.
Are you sure/
the bg7tbl devices simply pass their internal GPS's pps to their 1pps output?
(without improving it?)
So, people are buying it simply for the 10 MHz and not caring about the time being no more accurate than it is on a GPS? (arguably less accurate because of the apparent inability to set the cable delay, etc.)
Admittedly, the difference is such a small amount its challenging to measure it but still.
The difference isn't challenging to measure. Most modern scopes easely show 1ns/div. This is a screenshot of the difference between a 1PPS which uses the 10MHz output as a reference compared to the 1PPS coming from the BG7TBL:
(https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/?action=dlattach;attach=360918;image)
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Why doesn't he build in a limiter (sine to square wave converter) divide by 10,000,000, and allow adjustment of the rising edge to the UTC second?
Even a square wave (50% duty cycle/500 ms positive) would be adequate, as long as the rising edge came at the transition to the second.
Perhaps that one is the harder of the two to get right?
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Why doesn't he build in a limiter (sine to square wave converter) divide by 10,000,000, and allow adjustment of the rising edge to the UTC second?
Even a square wave (50% duty cycle/500 ms positive) would be adequate, as long as the rising edge came at the transition to the second.
Perhaps that one is the harder of the two to get right?
The biggest question is: is that 1PPS exactly right? IMHO the conclusion is that GPS isn't somehow good enough to transfer time with better than (say) 100ns accuracy. For a lot of purposes that is good enough.
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The ionosphere shifts kind of like waves in the ocean (it looks a bit like that and the time constant is not that dissimilar either) from one second to the next. Depending on the GPS, "the time" likely shifts with it.
You can see this motion in a scatter plot of your position in the three dimensions that leaves out time, or by plotting the three dimensions one on top of another in the vertical axis and time in the horizontal axis.
It helps greatly to tell the GPS that you are stationary so it can ignore the changes that clearly are inconsistent with a stationary or near stationary location. That's its job.
But you need a good signal, free of multipath, and you have to be able to tell the GPS to do that!
Ublox have multiple means of communicating to the GPS on their midrange models.. what amounts to the equivalent of multiple UARTs so it would be possible.
My guess is that BG7TBL is such a small customer that ublox "won't give him the time of day".
(Quite an appropriate colloquial English expression, as they go, in this case)
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BG7TBL should switch to Skytraq.
Skytraq would likely be the best match for his endeavors.
They perform better for me. As the best I can do as far as measurement is NTP performance compared to other NTP servers, I have no way of doing precise measurement with the GPIOs that I know of.
Somebody should write that software.
However, this GPS is connected to my Raspberry pi GPIO by a wire approximately 2 cm long. It was the shortest I could make it without making it structurally unsound.
The (NTP-via-ntpq) jitter measurement is always the same, some very low amount. ".004" I think.
The stats are always the same. Almost no variation.
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BG7TBL should switch to Skytraq.
...
The jitter measurement is always the same, some very low amount. ".004" I think.
The stats are always the same. Almost no variation.
Thanks for that. I hadn't looked into Skytraq before. The Venus precision timing receiver looks very nice:
http://www.skytraq.com.tw/products/Venus838LPx-T_PB_v2.pdf (http://www.skytraq.com.tw/products/Venus838LPx-T_PB_v2.pdf)
A search shows this board: https://www.tindie.com/products/nsayer/skytraq-venus838lpx-t-timing-gps-module-breakout/ (https://www.tindie.com/products/nsayer/skytraq-venus838lpx-t-timing-gps-module-breakout/)
Tom
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BG7TBL should switch to Skytraq.
I thought the whole thing about those boxes was they used a complete surplus GPSDO. As far as I've seen there's no smarts on the bit BG7TBL puts together. It is entirely reliant on a complete and self-contained GPSDO module sitting on a carrier board that just supplies power and some level conversion.
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They've got a CPLD and a micro doing stuff in the current versions, while the older versions were basically carrier boards/adapters for commercial modules, the new ones definitely are controlling the disciplining of the OCXO with on their own.
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Did anyone ever do a comparison between their bg7tbl gpsdo and a different reference to see if the output frequency is 10MHz? I'm using mine (version 2017-03-29) to feed a clock (date + time). Because that clock wanders compared to an ntp synchronised clock I measured the output frequency and it turns out my bg7tbl gpsdo is 1.5Hz too low! :wtf: Needless to say this thing starts to look more and more like a waste of money. :'(
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BG7TBL has several different GPSDOs. Only the first version had a known frequency error and it was off in the 1E-9 range. If you are 1.5 Hz, something is wrong... and that something could be the reference you are comparing it to.
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Is that an NTP synchronized clock thats synchronized to a GPS 1pps via kernel discipline, or is it running off the GPSDO 10 MHz?
They would likely be different it sounds -
With the caveat that I have still been too lazy to recompile my Raspberry Pi's kernel to get an extra two orders of magnitude with my plain GPS time server, I fully do expect that when i do, I will get much more accurate time from my GPSDO and its 1PPS than I do from my GPS. Even though its a good one.
However, lacking the so called kernel discipline its still accurate to better than a microsecond so I cant complain.
NTP connected clocks do have error. Various kinds of wander occur and can be characterized. So what you see is / are likely the combined effect of a number of different sources of error common to computers in that situation. Including clock and network latency. Thats far more likely.
I think "Chrony" is better than NTP in that respect. I'm planning to hook my GPSDO up to a machine I have that has a real ethernet card not a USB one, and real GPIOs and I'm also planning to switch my RPI to Chrony one of these days. Then I'll have two or when my desktop is running three sources of network time to serve as sanity checks for one another.
Did anyone ever do a comparison between their bg7tbl gpsdo and a different reference to see if the output frequency is 10MHz? I'm using mine (version 2017-03-29) to feed a clock (date + time). Because that clock wanders compared to an ntp synchronised clock I measured the output frequency and it turns out my bg7tbl gpsdo is 1.5Hz too low! :wtf: Needless to say this thing starts to look more and more like a waste of money. :'(
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Did anyone ever do a comparison between their bg7tbl gpsdo and a different reference to see if the output frequency is 10MHz? I'm using mine (version 2017-03-29) to feed a clock (date + time). Because that clock wanders compared to an ntp synchronised clock I measured the output frequency and it turns out my bg7tbl gpsdo is 1.5Hz too low! :wtf: Needless to say this thing starts to look more and more like a waste of money. :'(
Are you sure the NTP clock is as good? Usually network time is only good down to milliseconds or hundreds of microseconds because of the time it takes to query the server and the differing travel times - networks that need very precise network time usually have a local stratum1/2 reference and then are compensate for cable run length.
If you've got a real stable reference (and even a good OCXO will not be absolutely accurate without some sort of disciplining because of drift and aging) and a frequency counter to match up against, then I'd trust the measurement, but less than that.... I doubt the error is with the GPSDO (unless it's not GPS locked, in which case it can certainly drift).
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Did anyone ever do a comparison between their bg7tbl gpsdo and a different reference to see if the output frequency is 10MHz? I'm using mine (version 2017-03-29) to feed a clock (date + time). Because that clock wanders compared to an ntp synchronised clock I measured the output frequency and it turns out my bg7tbl gpsdo is 1.5Hz too low! :wtf: Needless to say this thing starts to look more and more like a waste of money. :'(
Unless my maths is wrong (wouldn't be the first time) 1.5Hz is 0.15PPM or about 13ms a day. How long a period did you measure it over and how did you compare it against your NTP synced clock?
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Did anyone ever do a comparison between their bg7tbl gpsdo and a different reference to see if the output frequency is 10MHz? I'm using mine (version 2017-03-29) to feed a clock (date + time). Because that clock wanders compared to an ntp synchronised clock I measured the output frequency and it turns out my bg7tbl gpsdo is 1.5Hz too low! :wtf: Needless to say this thing starts to look more and more like a waste of money. :'(
Are you sure the NTP clock is as good?
Yes, it is one from pool.ntp.org. The clock wanders off by several seconds within a couple of minutes and NTP and the RTC crystal driving the other clock are not that bad. OTOH I now realise that 1.5Hz on 10MHz is around 1ppm so the whole situation doesn't make much sense.
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That's so much error it doesn't make sense. Even my plain $7 GPS would have much less error than that.
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Did anyone ever do a comparison between their bg7tbl gpsdo and a different reference to see if the output frequency is 10MHz? I'm using mine (version 2017-03-29) to feed a clock (date + time). Because that clock wanders compared to an ntp synchronised clock I measured the output frequency and it turns out my bg7tbl gpsdo is 1.5Hz too low! :wtf: Needless to say this thing starts to look more and more like a waste of money. :'(
Are you sure the NTP clock is as good?
Yes, it is one from pool.ntp.org. The clock wanders off by several seconds within a couple of minutes and NTP and the RTC crystal driving the other clock are not that bad. OTOH I now realise that 1.5Hz on 10MHz is around 1ppm so the whole situation doesn't make much sense.
It turns out other parts of the software on the system are messing with the system clock every now and then. I didn't expect that.
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Once you have to look across an Ethernet network you lose precision because of the inherent latency of using a network. If you want precision you are better off distributing your 1PPS or 10 MHz signals via some simpler non-networked means.
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The new BG7TBL 10MHz GPSDO with a LCD Display
https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/112700839490?hash=item1a3d7e5642:g:TqQAAOSwPPpaOhYT (https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/112700839490?hash=item1a3d7e5642:g:TqQAAOSwPPpaOhYT)
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FWIW Leo Bodnar's unit from SDR-kits is about the same price and provides a choice of two output frequencies. Very useful for things that don't accept a 10 MHz input such as the SDRplay RSP2. Probably my next purchase after my VNWA 3EC arrives.
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Of the units listed in the OP, which would be the most desirable?
Are any much better than the others?
I'm looking for a GPSDO and really don't know much about them.
Would these BG7TBL units be considered the best bang for the buck or should I look elsewhere for a ready to go box.
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Hopefully when someone purchases the new unit; they can do a teardown.
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Of the units listed in the OP, which would be the most desirable?
Are any much better than the others?
I'm looking for a GPSDO and really don't know much about them.
Would these BG7TBL units be considered the best bang for the buck or should I look elsewhere for a ready to go box.
I'm very happy with this unit. I did the management mode and not had a single problem with my unit. I also added the 10mhz square wave output.
The existing units have the Star Management mode already completed.
https://www.ebay.com/itm/10Mhz-GPSDO-OSCILLOQUARTZ-OSA-OEM-GPS-GPSDO-10MHz-1PPS-STAR-GPS-Clock/262861459973?hash=item3d33c39205:g:sbYAAOSwh2xYAjrp (https://www.ebay.com/itm/10Mhz-GPSDO-OSCILLOQUARTZ-OSA-OEM-GPS-GPSDO-10MHz-1PPS-STAR-GPS-Clock/262861459973?hash=item3d33c39205:g:sbYAAOSwh2xYAjrp)
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I got one of his Star-4 based units a year ago. It did not have the management interface connected to the serial port. I added an external RS-232 interface and had been using it that way. Last week I went in and re-wired the internal serial port to the management interface.
Here is the ADEV, etc measurements on my Star-4 based unit. I used a TAPR TICC clocked by an HP-5071 cesium beam oscillator. The room temp varied over 2 degrees C and had no effect on the frequency output... the 8663 oscillator using in them is a very good oscillator and the "ATDC" versions of the Star-4 use their highest spec'd model.
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So that is substantially better than the TruePosition, right?
Are the ADEV graphs you posted of the TP on TimeNuts last year directly comparable to this one (were the conditions similar enough to be directly comparable?)
I could post them but since they are yours...
There were two that
I saw. The Star 4 based unit looks like it could be considerably better if those two charts are directly comparable to this one.
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Are the ADEV graphs you posted of the TP on TimeNuts last year directly comparable to this one (were the conditions similar enough to be directly comparable?)
I could post them but since they are yours...
The setup was the same. I don't remember how long the Truposition had been powered up... the plot showed 6 hours of data whereas the Star had 13 hours and had been on for a day.
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I got one of his Star-4 based units a year ago. It did not have the management interface connected to the serial port. I added an external RS-232 interface and had been using it that way. Last week I went in and re-wired the internal serial port to the management interface.
Here is the ADEV, etc measurements on my Star-4 based unit. I used a TAPR TICC clocked by an HP-5071 cesium beam oscillator. The room temp varied over 2 degrees C and had no effect on the frequency output... the 8663 oscillator using in them is a very good oscillator and the "ATDC" versions of the Star-4 use their highest spec'd model.
After I saw your message about the unit, I went and purchased that one. I'm been very happy with the unit. I would agree that the oscillator is very good.
-
There is one on the auction site which has a blue lcd screen and not listed in the OP.
I guess this must be the latest installment in this series of GPSDO's.
Has anyone done a teardown of this unit yet?
-
How is your Lady Heather 6 beta coming along, are you ready to release your code to the public?
First i've heard of this! Any available info links?
-
Hello,
New GPSDO 10 Mhz made in BG7TBL :
I bought this GPSDO 10 Mhz in aluminum box via EBay (or aliexpress) for +/- 98$ and I am very satisfied.
It can provide a square or sinusoidal wave by moving a component on the output.
Pins 14-15-16 Neo7 are open, but they can be arranged to vary the baud rate.
Edit : After verification, this new GPSDO - PLL bought $98 contains an OCXO, not a VCXO.
The metal case Ocxo becomes very hot after a few minutes of operation.
The deal is excellent !!
(https://zupimages.net/up/18/04/961p.jpg) (http://zupimages.net/viewer.php?id=18/04/961p.jpg)
(https://zupimages.net/up/18/04/dr8j.jpg) (http://zupimages.net/viewer.php?id=18/04/dr8j.jpg)
(https://zupimages.net/up/18/04/f130.jpg) (http://zupimages.net/viewer.php?id=18/04/f130.jpg)
(https://zupimages.net/up/18/04/jcid.jpg) (http://zupimages.net/viewer.php?id=18/04/jcid.jpg)
----
- https://www.eevblog.com/forum/testgear/new-gpsdo-bg7tbl/ (https://www.eevblog.com/forum/testgear/new-gpsdo-bg7tbl/)
Diabolo
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I'm using Ver 5 of Lady Heather with a Thunderbolt GPS. When I first invoked the L/H it came up with co-ordinates for probably KE5FX so in addition to changing the time zone for Perth in Western Australia I successfully changed the co-ordinates at which stage L/H now says there are no sats usable. Why - is it ?perhaps the fact that KE5's IP address still shows? How do I get rid of it as I'm connected to my PC via Com1.
I know my GPS antenna is OK as on another piece of equipment it shows 8 satellites currently available.
Before I made any changes L/H was showing 6 satellites OK.
Any help appreciated Merv VK6BMT
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Hi Merv,
Your lady heather configuration should not show an ip address when you are connected via a COM port.
When the program is active type ? and you will see all of the startup commands available (a lot of them!), you can change the COM port by simply typing /1 in your case, that should clear things up.
-
You are probably running the example configuration that connects to John Miles net connected Thunderbolt in Seattle.
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Anyone have any info on the oven that may be used on the latest BG7TBL GPSDO version 2017-12-15 with the LCD? Also, is there a preferred seller someone can recommended?
looking at this guy right here;
https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/202153437548?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649 (https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/202153437548?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649)
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Leo Bodnar Units rock! I have been using them non-stop and they are everything I could ever want (except maybe a little more flexibility on choosing the 2nd freq., but that may be my fault for not knowing how). Their new mini is about $150 USD plus shipping. I used USB to set mine up and from then on it runs on it's own off an old USB phone charger.
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The case on the newest bg7tbl GPSDO is IMHO, very nice looking. Solid.
I also am curious what manufacturer's oven is in there. Or maybe he is making his own? Seems like it would make sense for him at this point.
--------
Also, I am curious about the Leo Bodnar unit
It uses a TCXO, right - not an OCXO??
But more accurate than the ones timing GPS's have internally?
Leo Bodnar Units rock! I have been using them non-stop and they are everything I could ever want (except maybe a little more flexibility on choosing the 2nd freq.
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The case on the newest bg7tbl GPSDO is IMHO, very nice looking. Solid.
I also am curious what manufacturer's oven is in there. Or maybe he is making his own? Seems like it would make sense for him at this point.
Guess I'll be the guinea pig, got one coming. I'll post up some photos once it arrives.
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Hi Merv,
Your lady heather configuration should not show an ip address when you are connected via a COM port.
When the program is active type ? and you will see all of the startup commands available (a lot of them!), you can change the COM port by simply typing /4 in your case, that should clear things up.
Probably on windows? The windows version has two icons to launch Lady Heather. Most likely launched the one pre-configured for the IP connection.
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Hello,
After verification, this new GPSDO - PLL bought $98 contains an OCXO, not a VCXO.
The metal case Ocxo becomes very hot after a few minutes of operation.
The deal is excellent !!
(https://zupimages.net/up/18/04/961p.jpg)
Regards,
Diabolo
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It looks like a #2 Phillips could help in this case. >:D
-
Hello,
The case was opened on the post #495
Diabolo
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So many options and likely BS to filter on evilbay...
Anyone got one of these can confirm they have an amplifier to do the distribution or not?
https://www.ebay.com/itm/GPSDO-10MHz-GPS-Disciplined-Clock-3-sine-and-3-square-wave-2-1PPS-Send-GPS-ante/253375324294?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649 (https://www.ebay.com/itm/GPSDO-10MHz-GPS-Disciplined-Clock-3-sine-and-3-square-wave-2-1PPS-Send-GPS-ante/253375324294?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649)
(https://i.ebayimg.com/images/g/5iEAAOSw8vNaX3eQ/s-l1600.jpg)
(https://i.ebayimg.com/images/g/Uw8AAOSwLjxaX3g-/s-l1600.jpg)
-
Hello,
New GPSDO 10 Mhz made in BG7TBL :
I bought this GPSDO 10 Mhz in aluminum box via EBay (or aliexpress) for +/- 98$ and I am very satisfied.
It can provide a square or sinusoidal wave by moving a component on the output.
Pins 14-15-16 Neo7 are open, but they can be arranged to vary the baud rate.
Edit : After verification, this new GPSDO - PLL bought $98 contains an OCXO, not a VCXO.
The metal case Ocxo becomes very hot after a few minutes of operation.
The deal is excellent !!
Diabolo
Thank you for the teardown.
Have you tried the RS-232 yet?
What, specifically, does it provide?
Assume NMEA packet?
Can you send commands to it?
If so, what can you configure?
TIA.
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Hello,
The GPSDO-PLL only gives access to NMEA received data, since the RX pin is not wired.
- https://www.eevblog.com/forum/testgear/new-gpsdo-bg7tbl/ (https://www.eevblog.com/forum/testgear/new-gpsdo-bg7tbl/)
Diabolo
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Hi,
My unit looks the same. Q1 inverted the RS-232 signal and no pc terminal program could read NMEA data. The signal at R6 was normal, so had to pick it off there. Q1 is supposed to be a voltage level translator.
Thanks fot the photos.
Steve
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Well, "the proof of the pudding is in the eating", but so very few of us have the equipment to do anything even remotely approaching testing of these devices. ;)
To test them you need both a reference that is verifiably better than them, and a universal counter or similar, also of verifiable accuracy, locked to it!
Hello,
After verification, this new GPSDO - PLL bought $98 contains an OCXO, not a VCXO.
The metal case Ocxo becomes very hot after a few minutes of operation.
The deal is excellent !!
(https://zupimages.net/up/18/04/961p.jpg)
Regards,
Diabolo
-
Part of the fun of 'nuttery' be it freq or volt is getting the best you can while |O Double the $$ for an extra decimal place.......
Think I will take a punt on what I posted a few back as it ticks the boxes for me in small compact with multiple outputs. I know a few good local amateurs with some additional test gear to test against.
-
Anyone have any info on the oven that may be used on the latest BG7TBL GPSDO version 2017-12-15 with the LCD? Also, is there a preferred seller someone can recommended?
looking at this guy right here;
https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/202153437548?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649 (https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/202153437548?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649)
Would also like some more information on this one. I've been thinking about getting a rubidium oscillator but if I can get close with this unit that would also be nice.
-
A few pictures of my new BG7TBL GPSDO 2017-12-16.
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Well, "the proof of the pudding is in the eating", but so very few of us have the equipment to do anything even remotely approaching testing of these devices. ;)
To test them you need both a reference that is verifiably better than them, and a universal counter or similar, also of verifiable accuracy, locked to it!
The other option is to buy two of them and test them against each other - or even get three of them and do a tri-cornered hat measurement. There are also methods that don't require a very expensive counter, though if you use the two mixer approach you do need an offset oscillator which may require say a DDS generator which are are not that cheap. The cheapest approach would be to use a phase comparitor (e.g. a mixer) and monitor the output voltage but I think this would require calibrating which may then require another signal source.
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I just came across this article which contains measurements (a review) of the bg7tbl distribution amplifier and compares it to the G4HUPRF 8 channel distribution amplifier - I don't think it has been posted here before and it is worth a read:
http://www.reeve.com/Documents/Articles%20Papers/Reeve_10MHzDist.pdf (http://www.reeve.com/Documents/Articles%20Papers/Reeve_10MHzDist.pdf)
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Still a few views on the last generation of the BG7TBL GPSDO.
Everything is fine also connect to PC with RS 232 cable. U-Center and Lady heaters work easily with this device and the NMEA data is displayed in the software.
best regards
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UCenter can command the internal GPS!?
What does it enumerate as, what kind of ublox GPS chip is in there?
There is a banner when it first starts up, would you be able to capture it and paste it here?
Still a few views on the last generation of the BG7TBL GPSDO.
Everything is fine also connect to PC with RS 232 cable. U-Center and Lady heaters work easily with this device and the NMEA data is displayed in the software.
best regards
-
WWV!
Beating a GPSDO against WWV will derive a beat frequency. That may be impossible to hear (way too low) but the difference might be possible to measure, removing the effect of the ionosphere somehow.. (averaging over 24 hrs repeatedly somehow? 24 hrs because the delay between WWV and your QTH should vary depending on height of ionosphere, seasonal also varies by time of day, also solar flare activity changes it.. Ionosphere may add several hundred km to 'distance' between QTH and WWV or similar time station, varying by aforementioned patterns, but also fairly unpredictable in short term. (DCF77 etc)
Easiest to measure would be to use the GPS to drive a DDS and set the DDS to a frequency approximately 1 KHz above or below WWV, then measure the audio beat frequency output. (difference) then take the average.
WWV is extremely stable as its derived from an atomic clock and I am sure sanity checked by multiple methods.
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To test them you need both a reference that is verifiably better than them, and a universal counter or similar, also of verifiable accuracy, locked to it!
I would be more concerned about the short therm accuracy, i.e. phase jitter etc. Also the frequency regulation will most probably show some mid term oscillations depending on the design.
There are even GPSDO sold on eBay which don't even have an OCXO or at least a TCXO. So while a long term measurement would be most probably OK they could still be pointless as frequency normal.
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UCenter can command the internal GPS!?
What does it enumerate as, what kind of ublox GPS chip is in there?
There is a banner when it first starts up, would you be able to capture it and paste it here?
Still a few views on the last generation of the BG7TBL GPSDO.
Everything is fine also connect to PC with RS 232 cable. U-Center and Lady heaters work easily with this device and the NMEA data is displayed in the software.
best regards
Hello.
No. I wrote U-Center can display the NMEA data. The U-blox neo 7m could not be controlled at the moment.
Another problem I have noticed yet.
On my two notebooks (with docking station) The GPSDO is misinterpreted as any pointing device.
The cursor jumps over the display and menus are activated indiscriminately.
Currently, the set up only works on my old Core2Duo tower.
Jörg
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Any device that sends data to a Windows machine over a serial port can be misinterpreted as a serial mouse. There are various ways to fix that, but they often don't work very well. The best way to handle it is to disable the fake mouse in Device Manager.
Ed
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When the power first comes up, what is the text that appears in the RS232 right at the beginning?
It might look something like this..
:40:45 $GNTXT,01,01,02,u-blox AG - www.u-blox.com (http://www.u-blox.com)*4E
19:40:45 $GNTXT,01,01,02,HW UBX-M80xx 00080000 *43
19:40:45 $GNTXT,01,01,02,ROM CORE 2.01 (75331) Oct 29 2013 13:28:17*4A
19:40:45 $GNTXT,01,01,02,PROTVER 15.00*01
19:40:45 $GNTXT,01,01,02,GNSS OTP: GPS GLO, SEL: GPS GLO*67
19:40:45 $GNTXT,01,01,02,ANTSUPERV=AC SD PDoS SR*3E
19:40:45 $GNTXT,01,01,02,ANTSTATUS=DONTKNOW*2D
19:40:45 $GNTXT,01,01,02,LLC FFFFFFFF-FFFFFFED-FFFFFFFF-FFFFFFFF-FFFFFF69*3E
19:40:45 $GNTXT,01,01,02,RF0 dev ok*04
Note that that particular output is from a questionable "M8N" board that I bought on ebay. A genuine M8N would have both ROM and flash firmware revisions displayed, not just one. My board appears to lack the EEPROM it is supposed to have.
Also, it may have an OXO, not a TCXO.. Which is another move to save a few pennies.. Its understandable, as I paid around $20 for my module, very little.
But I dont use it. If I was going to do it over I likely would just buy the factory fresh ones from places like cgshop which are sure to be genuine. But, the one I would need to buy for what I would want to do, the M8T, would cost ~$65-70. And I would need two of them.
Hello.
No. I wrote U-Center can display the NMEA data. The U-blox neo 7m could not be controlled at the moment.
Another problem I have noticed yet.
On my two notebooks (with docking station) The GPSDO is misinterpreted as any pointing device.
The cursor jumps over the display and menus are activated indiscriminately.
Currently, the set up only works on my old Core2Duo tower.
Jörg
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Any device that sends data to a Windows machine over a serial port can be misinterpreted as a serial mouse. There are various ways to fix that, but they often don't work very well. The best way to handle it is to disable the fake mouse in Device Manager.
Ed
Thank you Ed.
I've been fighting for about half an hour with the crazy fake mouse.
In the end I won and it works now. Crazy!!
Thank you so much. Jörg
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When the power first comes up, what is the text that appears in the RS232 right at the beginning?
It might look something like this..
:40:45 $GNTXT,01,01,02,u-blox AG - www.u-blox.com (http://www.u-blox.com)*4E
19:40:45 $GNTXT,01,01,02,HW UBX-M80xx 00080000 *43
19:40:45 $GNTXT,01,01,02,ROM CORE 2.01 (75331) Oct 29 2013 13:28:17*4A
19:40:45 $GNTXT,01,01,02,PROTVER 15.00*01
19:40:45 $GNTXT,01,01,02,GNSS OTP: GPS GLO, SEL: GPS GLO*67
19:40:45 $GNTXT,01,01,02,ANTSUPERV=AC SD PDoS SR*3E
19:40:45 $GNTXT,01,01,02,ANTSTATUS=DONTKNOW*2D
19:40:45 $GNTXT,01,01,02,LLC FFFFFFFF-FFFFFFED-FFFFFFFF-FFFFFFFF-FFFFFF69*3E
19:40:45 $GNTXT,01,01,02,RF0 dev ok*04
Hello.
No. I wrote U-Center can display the NMEA data. The U-blox neo 7m could not be controlled at the moment.
Another problem I have noticed yet.
On my two notebooks (with docking station) The GPSDO is misinterpreted as any pointing device.
The cursor jumps over the display and menus are activated indiscriminately.
Currently, the set up only works on my old Core2Duo tower.
Jörg
Hello cdev.
I'll take care of the information tomorrow.
I think you mean the text console in the U-Center.
Sorry, I'm only a beginner with this software.
Is there a better solution for this device than the small standard antenna?
Jörg
Now I have the information from the U- Center terminal.
??:??:?? $GPTXT,01,01,02,u-blox ag - www.u-blox.com (http://www.u-blox.com)*50
??:??:?? $GPTXT,01,01,02,HW UBX-G70xx 00070000 *77
??:??:?? $GPTXT,01,01,02,ROM CORE 1.00 (59842) Jun 27 2012 17:43:52*59
??:??:?? $GPTXT,01,01,02,PROTVER 14.00*1E
??:??:?? $GPTXT,01,01,02,ANTSUPERV=AC SD PDoS SR*20
??:??:?? $GPTXT,01,01,02,ANTSTATUS=DONTKNOW*33
??:??:?? $GPTXT,01,01,02,LLC FFFFFFFF-FFFFFFFD-FFFFFFFF-FFFFFFFF-FFFFFFFD*2E
I hope it helps you. Jörg
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Note that that particular output is from a questionable "M8N" board that I bought on ebay. A genuine M8N would have both ROM and flash firmware revisions displayed, not just one. My board appears to lack the EEPROM it is supposed to have.
Also, it may have an OXO, not a TCXO.. Which is another move to save a few pennies.. Its understandable, as I paid around $20 for my module, very little.
[/quote]
The documentation from the manufacturer confirms, that only the version with suffix "N" has a flash. My Neo 7 "M" merely a ROM .
A TCXO, but not a OCXO, is only in the version "N". Model "M" has a simple Quartz controlled Oszilator.
Jörg
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For what it's worth, the actual PPS output stability is almost identical across the ublox line, regardless of variant or temperature compensation on the oscillator. I've tested close to half a dozen ublox branded modules as old as the LEA 5T and as recent as the M8T and the PPS output is essentially identical. Of course there are different output options on the more recent timing grade devices that would be more impacted by oscillator stability, but the PPS is the same.
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For what it's worth, the actual PPS output stability is almost identical across the ublox line, regardless of variant or temperature compensation on the oscillator. I've tested close to half a dozen ublox branded modules as old as the LEA 5T and as recent as the M8T and the PPS output is essentially identical. Of course there are different output options on the more recent timing grade devices that would be more impacted by oscillator stability, but the PPS is the same.
A few questions for you, given your experience with the ublox...
What is the behaviour of the pps signal if no GPS is present ? is there good holdover ? is there any pps at all ?
thanks
Tim
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The PPS output is only active when the signal is locked - there may be a holdover on the order of seconds or a minute, but it also may be that their more modern chipsets just have a bit better signal reception and don't lose reception often.
Here's a couple pics of about 50k seconds of recording of a Neo 7n module, measured with a 100ps resolution 12 digit/s counter referenced to a rubidium oscillator locked to a resolution SMT gps PPS. The other modules in the series I measured basically exhibited the same behavior - same adjustment step size, similar base frequency drift, always converged fine to exactly 1s with longer averaging times. Behavior basically looked the same on a Neo 7M, Neo 7N (TCXO), Lea 6T, and Neo M8T. No real reception issues with any of them, so after at least 12h of having a lock, I don't think any of them had a drop in the 50k seconds or so I measured each for.
Reminds me, I need to write up the findings and actually get around to posting it, measured 10 or so module's PPS signals to see how well they fared.
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Re. Post/Reply #514 & #517
Still a few views on the last generation of the BG7TBL GPSDO.
Everything is fine also connect to PC with RS 232 cable. U-Center and Lady heaters work easily with this device and the NMEA data is displayed in the software.
best regards
Hello Jorg: Could you please tell us about the Frequency display (for the 10 MHz freq.) on the front panel LCD. What does it report when 1. the GPSDO is initially turned ON, 2. as it is warming up and getting locked, and finally 3. after it is locked with a 4D fix/tracking. I would like to understand and appreciate its use, capability, and value.
Thank you so much, Ted
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Hello Ted.
First, in the bottom line, the device displays "GPS not fix".
Later, the 10 MHz is displaed, with a deviation of about 0.0120 Hz.
After about two or three hours, the letter "L" is displayed as the first character. Then only the last point varies.
I suppose it means the PLL is locked.
Regards. Jörg
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Hello Ted.
First, in the bottom line, the device displays "GPS not fix".
Later, the 10 MHz is displaed, with a deviation of about 0.0120 Hz.
After about two or three hours, the letter "L" is displayed as the first character. Then only the last point varies.
I suppose it means the PLL is locked.
Regards. Jörg
So what is the internal frequency counter referenced to then?
Sent from my SM-G900I using Tapatalk
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Re. Post Reply #531
Hello Jorg: This is good information. Thank you very much! I expected though that after a few hours the displayed frequency would be between 9,999,999.999,9 and 10,000,000.000,1. That is, if the frequency of the GPSDO is locked within the expected accuracy of the system. Although this here may be due to a low received GPS signal level, as it seems that your unit's signal level looks to be marginal. I say this because your Rx Signal Level indication on the LCD only shows a partial to full first bar, vs having all four bars (as shown on the eBay seller's picture of the LCD). Anyway you may want to see if your GPS antenna is appropriately located for good reception of multiple GPS satellites simultaneously. I have my GPS antenna mounted on the peak of my roof so that it has a full view of the sky. If you have a limited view (such as with the antenna on a outdoor window sill) the GPS reception can be heavily compromised
Thanks again for the information and pictures. And by-the-way I just ordered one thanks to data you provided. Cheers, Ted
Edit: It is possible that the "L" before the "10 MHz" freq. display will go away (?) once a full and stable Lock is obtained. I'm guessing that this may occur because I don't see the "L" on the ebay seller's picture of his unit (apparently with a solid Rx. signal strength and a correct 10,000,000.000,0 Hz resultant frequency). I won't be able to check this out myself until my unit gets here in about 30 days. So it will be interesting to hear what your unit does when you get a decent signal level into it.
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Hello Ted.
First, in the bottom line, the device displays "GPS not fix".
Later, the 10 MHz is displaed, with a deviation of about 0.0120 Hz.
After about two or three hours, the letter "L" is displayed as the first character. Then only the last point varies.
I suppose it means the PLL is locked.
Regards. Jörg
So what is the internal frequency counter referenced to then?
Sent from my SM-G900I using Tapatalk
The frequency error display is calculated by OCXO vs GPS lock phase delta.
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Since I still dont have my antenna set up outdoors properly, I have had good luck doing two surveys.
(note I dont have a bg7tbl gpsdo, I have a different one but I think this applies to all of them that use the TRAIM technique.)
Anyway, I do a coarse survey with the antenna outdoors and as perfect a sky view as I can. Then I do a second survey with the antenna in a window. If I try to do the first survey with the antenna indoors at a window it doesnt work, the first survey has to have almost a perfect antenna. But it will do the survey adequately well if its the second time, and close to the first location.
That may be all you need to get a much better signal.
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Hello everyone. I have some recent pictures in chronological order. In fact, I currently have only patch antenna indoor at the window. I can only see the south-west direction.
This is not optimal. I know. At the moment, nothing else is possible. For the frequency accuracy it should suffice. But I have already experienced, that the exact 10 MHz are more likely to be displayed, befor the "L" is displayed. Just like the ebay seller.
After about 3 hours, the display will only vary by +/-1 digit around the 0. Also in this case, the letter "L" will be displayed continues.
Best regards. Jörg
.
-
Jorg, did I correctly interpret your posts and does that new unit, with the LCD display. have a Trimble OCXO? I am hoping to use one as a standard in the home lab, but will not be getting it in the next few weeks so who knows, might find a cheap second hand GPSDO. Either that or a rubidium oscillator. Still not sure, being able to say I have an atomic clock at home is also cool....
-
Jorg, did I correctly interpret your posts and does that new unit, with the LCD display. have a Trimble OCXO?
Yes, of course. The photos are original.
-
Re. Post 'Reply #531, by Jorg:
Hello everyone. I have some recent pictures in chronological order. In fact, I currently have only patch antenna indoor at the window. . . . . . Best regards. Jörg
Hello Jorg: Thank you for the LCD photo series presentation of your GPS results. This is great, and I like that the "L" stays there as long as the GPS is Locked, and apparently with a 4D Fix. I'm even happier now that I ordered one of these, as I have been interested in it ever since finding it on ebay (Reply #484, https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg1379350/#msg1379350 (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg1379350/#msg1379350)). You provided the confidence for me that this is a very nice unit, and that now I won't have to keep my computer connected to my GPS to know its status. The LCD now says it all (enough anyway) for me. And of course I will now be able to use a fully compatible GPS application to see its complete status with time offset error, etc.
You have done a lot of work here for us. Thanks and cheers, Ted
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I now have a new antenna. It still has a patch antenna, but with better quality than the simplest version. Of course, it is also a little more expensive. It's in the same place as before. Inside at the window, with a view to the south-west. The quantity of the satellites is much higher. Allocation for navigation is not optimal, but not bad for indoor operation. The GPS fix has no loss.
For frequency accuracy it should be good.
Jörg
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Re. Post 'Reply #531, by Jorg:
Hello everyone. I have some recent pictures in chronological order. In fact, I currently have only patch antenna indoor at the window. . . . . . Best regards. Jörg
Hello Jorg: Thank you for the LCD photo series presentation of your GPS results. This is great, and I like that the "L" stays there as long as the GPS is Locked, and apparently with a 4D Fix. I'm even happier now that I ordered one of these, as I have been interested in it ever since finding it on ebay (Reply #484, https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg1379350/#msg1379350 (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg1379350/#msg1379350)). You provided the confidence for me that this is a very nice unit, and that now I won't have to keep my computer connected to my GPS to know its status. The LCD now says it all (enough anyway) for me. And of course I will now be able to use a fully compatible GPS application to see its complete status with time offset error, etc.
You have done a lot of work here for us. Thanks and cheers, Ted
Hello, Ted. My pleasure. I've also read a lot in this forum.
If I have the opportunity, I would also like to contribute.
Maybe you have a way to accurately check your BG7TBL with good equipment. Unfortunately, I can`t make any statements about absolute accuracy at the moment.
Now, i have a part of the user manual for the display messages.
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Jorg, which antenna are you using now? How does it differ from the one supplied?
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Jorg, which antenna are you using now? How does it differ from the one supplied?
It's a ADACTUS ADA-A720-S. Double LNA with intermediary filter.
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Found a PCTEL GPS L1 antenna for cheap on eBay;
http://www.antenna.com/apg_search_new.html?type=details&id_num=11589 (http://www.antenna.com/apg_search_new.html?type=details&id_num=11589)
This looks like a great antenna to mount on the edge of the roof, nice pass band filtering and for less than $30. Spec'd to work on 3.3v.
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Looks good for the price.
But with the best will, I live in an apartment house. Antennas in an optimal place are hardly possible. Unfortunately, it must remain a compromise,
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The new BG7TBL 10MHz GPSDO with a LCD Display
https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/112700839490?hash=item1a3d7e5642:g:TqQAAOSwPPpaOhYT (https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/112700839490?hash=item1a3d7e5642:g:TqQAAOSwPPpaOhYT)
I just received one of these this week. Seems to be nicely designed and constructed. I have its output being measured by my modified Fluke 7220, which I upgraded to an OCXO using my own adapter board and VFC reference design (coincidentally, the same model Trimble 65256 used in the BG7TBL). The Fluke can display down to 0.1Hz, and that's right where it sits - rock solid on 10.0000000+1. Since that's my only other precision reference, I can only say the BG7TBL (dated 12/2017) at least agrees with my OCXO.
My OCXO (in the Fluke) was calibrated by the seller and I used the same VFC value he referenced. Comparing its output with WWV here isn't super accurate - I can only do it by looking at amplitude or listening for a beat, but I can't detect any difference between them, meaning that I feel comfortable assuming my OCXO is at least good down to less than 0.1 HZ.*
I'm going to put them both on a scope and measure phase changes over time. I'm feeling pretty confident in what's coming out of the BG7TBL, so I'll trigger off that. :)
The antenna is the one supplied with the GPSDO. It's placed indoors, on a window sill up against the glass. The GPSDO locked right away and seems to stay locked.
*(My method of calibrating my Fluke's OCXO using WWV is to set the my HF receiver to 10 MHz USB, then detune by 1 KHz (I'll hear a 1 KHz tone generated by the SSB BFO). With a small "antenna" on the clock output of the Fluke, I can get a signal level in the ballpark of what I'm receiving from WWV. Both signals then have the same tuner offset on the receiver, so if there's any difference between the sources, I'll either hear it (if large enough difference) or see it fluctuate on the S-meter. Of course, if there's any fading from WWV, it will confound the measurement. If I don't see or hear any changes over more than 10 seconds, that should be less then 0.1 Hz. It's a bit tedious method, but it's all I had (and why I bought the GPSDO). Note that even though my receiver has been zero-beat with WWV, it doesn't really matter, since both WWV and the OCXO output meet the same receiver offset and same USB BFO oscillator.)
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Re. Post 'Reply #546'
Hello gr8tfly: I assume from the picture of your New BG7TBL LCD GPSDO's front panel that you had "L" displayed in front of the frequency display while it was in the 'Locking process' with a 3D Fix. And then after it achieved a full Lock with exactly 10,000,000.000,0 Hz displayed, that the "L" then when away. Is this what happened?
Thank you for your assistance, and congratulations on getting your new GPSDO. You will now be able to use it as frequency calibration standard for everything else you have there. :clap: Cheers, Ted
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Once it displays the "L", I only see +/= ~0.0002, and that's just once in a while. Mostly, it's 10.0000000000, which is fun, especially with my counter also displaying "0"s. It's like a jackpot. :)
I have some short periods when I get "GPS NO FIX", but that's because there's a house within about 20' of the window. Not ideal, but the window is right at my work table so what'cha gonna do... Anyway, when the signal come back, the display immediately shows the "L", so it might be an accuracy indication too. The output clock does not change as it transitions from "NO FIX" to "L10.xxx", as you would expect.
One more thought on the "L": I just remembered that the LED for GPS LOCK lights long before the "L" shows up on the display. So, I'm pretty sure it's just an indication that the controller has driven the OCXO to where it considers it within some tolerance. The documentation only seems to say something about accuracy. In the FAQ, it says something about it meaning the frequency error is less than 0.000x.
Sometime soon I'll hook up the RS-232 port and try some of the software packages, VisualGPS and Lady Heather, in particular.
I'm sure you'll enjoy the GPSDO when it arrives. Seems like it took a couple of weeks to central California, if that's any guidance. Have fun!
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Re. Post - Reply #548
Hello gr8tfly: Thank you for the information, although can you please confirm that the "L" is NOT displayed in front of the frequency when it is exactly 10000000.000 as shown in your photo? I just want to make sure that this particular photo isn't simply a fluke without the "L.
I take it that you received instructions or specifications with your unit(?). If so, that sounds nice, as the lower cost stuff from China (not that $200 is anywhere near being low cost, except here - for what you get, it is) very seldom is supplied with any user info. By the way I'm very grateful for all the equipment and components that are available from China. And I'm a Rigol Test Equipment fan.
Yes, I'm looking forward to receiving the new BG7BTL GPSDO. It has been held in lingo for the last couple of days. I received a "It Has Been Shipped Notice' with a China Post Tracking Number. But all I can find out about it is that the number was assigned, but that it has not yet been received by China Post. And I expect that it won't be until the Chinese Spring Holiday celebration is over (I believe some tine after Feb. 21). I'm not new to GPSDO, as I have used them for about 20 years. I particularly like this new one because you can tell at a glance its basic state, without having a computer connected to it. Cheers, Ted
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Doh. If it were a snake it'd bit me. You know what they say about having a second set of eyes check something...etc. I totally missed the fact the "L" was not displayed at that time.
No, it definitely does display an "L" when it's xx0.0000. Of course, the question is how it decides to do that. It may be based on power-on time, as it mentions something about 5 hours in the [limited] documentation.
I've attached a few more photos. One from a couple of days ago, and a couple from just a few minutes ago. One of the latter is at xx0.0000, the other is xx0.0001 Hz - both display the "L" flag.
Also, I've attached the .doc the vendor sent me (I don't think there's any copyright issue, since we both purchased the product - call me paranoid?). I'm just about done removing the Chinese characters, as it improves readability. The English "translation" alternates lines with the Chinese, so I thought it worth a few minutes of editing to make myself an all English version. I can post that here later on too.
The user's manual has a nice block diagram. It also describes a command mode whereby you can change things like how it displays the time and a variety of different clock representations. There are some pads that need to be jumpered to enable the mode. I looked at the various display options, but I'm pretty happy with the default.
It's been ages since I've had a GPS connected to my computer (like almost 20 years), so I'm looking forward to playing around with Lady Heather and perhaps VisualGPS. I have some terminal apps too, so I can manually capture the NEMA output.
Equipment wise, I suppose I'm a Siglent fan, at the moment. :) I think it's been almost 2 years now since I bought a Siglent SDS1102-X. Prior to the DSO, my personal scope was a Tek 465b, which, I must say, I've quite a fondness for, but it's just too darn big and heavy for me these days and haven't used it in years). So, comparatively, I'm pretty blown away by the features the Siglent has - especially for (at the time) $499.
As you can see in the pic from a couple days ago, I have one of the inexpensive DDS generators. I just got tired of the instability and a bit of hash it has (I'm spoiled by years in the lab with unaffordable high-end gear) and over the holidays replaced it with a Siglent SDG-1032X. Most of my RF experimenting is in HF, plus it has all the modulation modes I could want. Of course, it was a whole 25 Hz off (measured with my Fluke). I could have used the output from the Fluke, but nooooo - this was a great time to get a GPSDO! :)
Take care!
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'VisualGPSView is a very nice, easy setup, and to use program. It is Freeware and available at: http://www.visualgps.net (http://www.visualgps.net) Note: It may be require opening the RTS {7} and CTS {8} lines & connecting them together on the PC side. A DIY 9 Pin F to M adapter can be fabricated for this function and plugged into the GPSDO's RS232 connector.
If you can get Lady Heather working with your unit you may be able to get much more info using it. I don't know If the BG7TBL LCD GPSDO supports the Lady Heather functionality enough or not to be useful.
Edit: I deleted everything else that I originally had here because it is all covered better in KJ7E's post Reply 533 (below) in the BG7TBL LCD-GPSDO Manual that he provided. Wow, what a fantastic job on the manual translation. Slight touch up - In a couple of hours may be. . .
Thanks very much KJ7E Cheers, Ted
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Slight touch up on the BG7TBL LCD V1 manual English translation, see the attached PDF below.
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Wow! Thanks so much for doing this. Much nicer than what I had started doing (I hadn't done any clean-up of grammar, etc., only removing the interleaved language changes for clarity).
Chuck
WB6KDH
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Here's another shot of the main board that's not cropped. I realized the reflections around the ublox in my first attachment blew out the jumpers a bit. I was more focused on getting all the main components, especially the Atmega's, part numbers to show up.
Chuck
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I notice there is a jumper to select either 3.3v (default) or 5v for the active GPS antenna near the Ublox chip. I've added this to my working copy of the manual. Since my unit somewhere between Shenzhen and the US, kind of hard to do any better or verify the info. I made extensive use of Google Translate which does a better job of translating the Chinese characters to English than the provided English subtext then tried to make it a bit more readable. I cant verify the display commands, but I think I fixed a few typos from the original.
Chuck, I saw your call in one of your photos and looked you up already, I see your not too far from me. I'm just over the hills to the East.
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The 2017-12-16 BG7TBL LCD GPSDO came in last week. While I was able to get a usable GPS lock with the supplied antenna near the window, it was marginal at best. Found a PCTEL GPS-TMG-HR-26N antenna brand new on eBay for $30, got it mounted this afternoon.
http://www.antenna.com/apg_search_new.html?type=details&id_num=11589 (http://www.antenna.com/apg_search_new.html?type=details&id_num=11589)
I would have preferred to put the antenna on the roof with a clear 360 deg view, but due ladder issues I settled for a secondary location with a good 270 deg view (obstructed view to the north east). I was able to getaway with a single 50' run of LMR-240 so feed line loss is not bad at all. The PCTEL antenna spec says it will run down to 3.3v, but I moved the PCB jumper to 5v anyway. Of course this blows away the supplied antenna, 15 sats being tracked many with SNR better than 40db (according to Lady Heather).
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/F78FE5B2-E71C-4BC2-81FC-C30F29969456.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/F78FE5B2-E71C-4BC2-81FC-C30F29969456.jpg.html)
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/D364AE8A-34B0-44FC-AFF6-80834DB5DF52.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/D364AE8A-34B0-44FC-AFF6-80834DB5DF52.jpg.html)
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Hello owners of the new BG7TBL LCD-GPSDO (Dec. 16, 2017):
I received my new LCD GPSO yesterday (only 11 days after receiving notice of shipment from China; TNX - flyxy2015) and Ii'm interested in changing it to display time in EST, and reference frequency in the 000.00ppb format. Which I believe requires the program $ GPGTC, 2 BJT +0500T *. I'm prepared to send a email to BG7TBO and ask him for some assistance. But, I thought that I should check here first.
Basic Questions: 1. Where should we connect a RS232 Terminal emulator (PC), as it won't be the front panel DB9 RS232 connector, as it is internally only connected to the NEO-7M GPS receiver? 2. Is there a jumper we have to add, or remove to, put the unit into the programming mode? Of course, there is a open spot for a 10 pin connector next to the ALTER MAX II, so this is a good possibility. I have a few other small points to ask, or simply work out when I get answers to these two questions.
Thanks for any assistance, and cheers, Ted
Edit Feb. 28, 2018: Obviously BG7TBL intended for us to be able to make these kind of changes to his unit, or he wouldn't have provided us with the appropriate software information for doing so in the Instruction Manual. Therefor I will send off the email I prepared for him and it may help him to think about adding the missing details (if he hasn't already) in his Manual. And after all, we should receive the missing details directly from BG7TBL, and not have to second guess it.
I used the photos provided here by 'gr8tfly', WB6KDH (Thank you Chuck) to have a brief look at the design. I would normally have taken my unit apart and stated to figure this out myself, but I'm recovering from a illness which is slowing me down. I hope and expect to be back to normal in a few more days. By the way I feel that BG7TBL's New LCD-GPSDO is a awesome unit, inexpensive for what it does, and a operational leap forward beyond the pack for the currently available GPSDOs.
Second Edit: I sent the email message to BG7TBL at bg7tbl@gmail.com and it bounced back with a fatal error. I then resent to bg7tbl@qq.com, and bg7tbl@126.com, as if these are going to work (?). They certainly look strange, so I don't have high expectations for them either. Anyway if, and when, I hear from him I will post the reply here for everyone. And I of course suggested that this missing information should be added to his manual.
Of course, it is possible that we don't have his current manual. If you see a newer version of the Manual please post it here. And if you have a email address that looks like it could be valid please let me know. Thanks, Ted
PS If none of this pans out I will ask my seller (who also provided me with a Manual PDF file per my request) for assistance. By the way these last two emails have not been bounced back yet, and it seems strange that these (@qq.com & @126.com) could be valid!
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Ted,
Did you notice that the email address you listed had the B & G reversed? Also, which eBay seller did you buy it from?
Bill
K1FPV
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Ted,
Did you notice that the email address you listed had the B & G reversed? Also, which eBay seller did you buy it from?
Bill
K1FPV
Thank you Bill, and No I didn't notice that, but I just checked and the actual email I sent was correct. So my error was just in the above posting. I actually wish I had made the error there, because then I would at least have a good second shot getting a message to him. The other two addresses are just too ridiculous to be valid. Although they didn't bounce back to me for what ever reason.
My seller was flyxy2015 and I listed him in the first sentence of my original posting. His ebay link is > https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/112700839490?hash=item1a3d7e5642:g:TqQAAOSwPPpaOhYT (https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/112700839490?hash=item1a3d7e5642:g:TqQAAOSwPPpaOhYT) I believe that he still has the best price, and very quick delivery to Canada and USA for these units. And to date he has sold 17 of these. I will waiit until tomorrow to send him a message asking if he can assist with this by passing my message on, and checking to see if there is a newer version of the Instruction Manual available now. This is the first decent manual that I have seen for the BG7TBL GPSDOs. So I guess we are lucky to have even what we have. Worst case, we should be able to figure this out, although I admit that I'm a little hesitant risking possibly tanking my unit. As we don't even know at this time if he even implemented the capability to alter the LCD display format via RS232 re-programming. :palm:
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The block diagram shows that the OCXO is driven by a PWM signal. Does anyone have phase noise plots on the 10 MHz output signal?
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The block diagram shows that the OCXO is driven by a PWM signal. Does anyone have phase noise plots on the 10 MHz output signal?
The signal is also run through a low pass filter;
http://www.ke5fx.com/gpscomp.htm (http://www.ke5fx.com/gpscomp.htm)
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Continuation of my post Reply #557 above
I received a reply from my email to BG7TBL asking him about the RS232 programming. His unedited reply is below in bold:
hello.. first inside jumper connect togethet..then connect com port..last send command... tomorrow i will tell you send which command..good night..bg7tbl
Kind of brief to say the least, because I asked specific and detailed questions. Basic simplified re-cap of questions follow:
1. Where should we connect a RS232 Terminal emulator (PC), as it won't be the front panel DB9 RS232 connector, as it is internally only connected to the NEO-7M GPS receiver? 2. Is there a jumper we have to add, or remove to put the unit into the programming mode? Of course, there is a open spot for a 10 pin connector next to the ALTER MAX II, so this is a good possibility.
Edit - Here is what to do: The jumper location is on the Main PCB directly behind the 3 Front Panel LEDs, and between a vertically mounted 1000uF, 10V electrolytic capacitor on the PCB. I soldered two Jumper pins here. Store a Jumper on one pin for 'Normal Mode', and put it across both pins for the 'Test Mode' (Pgm). The Front Panel 'RS232' connector is also used for programming {w/Jumper in Test Mode}. You only have to remove 2 screws each from the upper Front/Rear Panels to pull the cover up and off for access to the Jumper. Of course you will need to remove the Main PCB/Front Panel Ass'y to solder the jumper pins in place on the bottom of the PCB.
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Hate it when new toys arrive part way into an existing project ;D
Will add a new thread and teardown when I get a chance but I like the form factor for a start :-+
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I just received the latest 'BG7TBL LCD-GPS DISCIPLINED CLOCK, USER GUIDE V1.1'. This came directly from BG7TBL, and it replaces version 1.0 that we currently have. This manual has some additional information on the Programing process in the form of text and photographs, including the 'Test Jumper', etc. He also describes the use of programming Terminal emulation software.
I believe that it also helped to ask my eBay seller (flyxy2015) for assistance in this matter, and he has been very helpful with my inquiries, and provided me with the first manual, V1.0, via a email attachment. Oh yes, he also just sent me a email message asking if I had any questions. This is very nice service to get from a eBay dealer.
Note The Manual exceeded the maximum file size of 1,000kb, so I had to split in half, for item # 1., and 2. DOC files. You can copy and paste them together into a new Word (or equiv.) .doc file. Or work with the two files that is too much for you. If you have issues doing any of this, or whatever, send me your email address via a PM, and I will email the original file to you.
Cheers, and enjoy, Ted
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The 2017-12-16 BG7TBL LCD GPSDO came in last week. While I was able to get a usable GPS lock with the supplied antenna near the window, it was marginal at best. Found a PCTEL GPS-TMG-HR-26N antenna brand new on eBay for $30, got it mounted this afternoon.
http://www.antenna.com/apg_search_new.html?type=details&id_num=11589 (http://www.antenna.com/apg_search_new.html?type=details&id_num=11589)
I would have preferred to put the antenna on the roof with a clear 360 deg view, but due ladder issues I settled for a secondary location with a good 270 deg view (obstructed view to the north east). I was able to getaway with a single 50' run of LMR-240 so feed line loss is not bad at all. The PCTEL antenna spec says it will run down to 3.3v, but I moved the PCB jumper to 5v anyway. Of course this blows away the supplied antenna, 15 sats being tracked many with SNR better than 40db (according to Lady Heather).
(http://s241.photobucket.com/user/wsmc551/media/Elecronics/F78FE5B2-E71C-4BC2-81FC-C30F29969456.jpg.html)
(http://s241.photobucket.com/user/wsmc551/media/Elecronics/D364AE8A-34B0-44FC-AFF6-80834DB5DF52.jpg.html)
Hi kj7e,
Which of these suppliers did you go with (or did you get your GPSDO from another supplier)?
diyelecmall108
https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/202153437548?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649 (https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/202153437548?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649)
flyxy2015
https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/112700839490?hash=item1a3d7e5642:g:TqQAAOSwPPpaOhYT (https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/112700839490?hash=item1a3d7e5642:g:TqQAAOSwPPpaOhYT)
Did the supplier you picked for the GPSDO include an antenna (I didn’t see any mention of an antenna included in the above links but maybe I missed it).
Still happy with the PCTEL antenna?
Also, it sounds like have been using Lady Heather? Did you also try VisualGP? If so, any thoughts on how they compare in terms of ease of use and functionality?
Thanks!
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Hi kj7e,
Which of these suppliers did you go with (or did you get your GPSDO from another supplier)?
diyelecmall108
https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/202153437548?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649 (https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/202153437548?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649)
flyxy2015
https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/112700839490?hash=item1a3d7e5642:g:TqQAAOSwPPpaOhYT (https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/112700839490?hash=item1a3d7e5642:g:TqQAAOSwPPpaOhYT)
Did the supplier you picked for the GPSDO include an antenna (I didn’t see any mention of an antenna included in the above links but maybe I missed it).
Still happy with the PCTEL antenna?
Also, it sounds like have been using Lady Heather? Did you also try VisualGP? If so, any thoughts on how they compare in terms of ease of use and functionality?
Thanks!
I got mine from diyelecmall108. Yes, included a basic antenna and a wall wart power adapter.
The PCTEL antenna is way, way better than the supplied antenna. I also noticed the GPSDO lock holds much more stable in the last displayed digit with the improved signal strength.
Signal strength plot below, note the antenna has an obstructed view to the north east.
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Thx - do you have any recommendations/preferences on software?
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Also, it sounds like have been using Lady Heather? Did you also try VisualGP? If so, any thoughts on how they compare in terms of ease of use and functionality?
Functionality wise... there's no comparison. Heather is around 100,000 lines of code. There is a LOT of functionality in there. Heather can fully monitor, configure, and control over three dozen different devices. Visual GPS is just a monitoring program. But, you don't need to use any the fabcy-pants functionality... just fire up the program, sit back and relax, and watch das defaulten blinkenlights. You will see just about anything you want on one screen or can zoom various items to full screen with a click of the mouse.
Heather's user interface does not use those new-fangled drop down menu thingies, etc. It uses an old fashioned keyboard driven menu system. No precious screen space is wasted with menu bars, window decorations, etc. Type the first letter of a command and a menu appears in the plot area showing the various commands you can do from that menu. Press SPACE to see how the various commands are grouped. Don't like it? Too millennial to use anything but drop down menus? Well... Heather is open source... knock yourself out.
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Cracked the case on my GPSDO open tonight and plugged it in. Power consumption dropped to about .6A at 12V but is rated to 24V. Seemed to get a lock fairly quickly but I didn't time it or try and get it hooked up to the PC.
Decided not to start a thread for it as it shares apart from the custom lower board fairly much all the same internals as most of these.
The lower Board on mine is badged amoj1010 the same as the Ebay seller so I am assuming it is his board. eBay auction: #https://www.ebay.com.au/itm/GPSDO-10MHz-GPS-Disciplined-Clock-3-sine-and-3-square-wave-2-1PPS-Send-GPS-ante/253375324294?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 Arrived very quickly after Chinese New Year wrapped in EPP foam and with a couple of freebie extras :-+ Sorry but the shot of the lower board is blurry I will take a better one tomorrow.
Bit of ringing on the square wave with a 50 ohm load and the sine wave seemed solid.
Now I feel like the man with two watches but the frequency was very stable over the course of a few hours but I will get mine compared to a HAM mates and have a play with the software and some longer testing.
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Note The Manual exceeded the maximum file size of 1,000kb, so I had to split in half, for item # 1., and 2. DOC files. You can copy and paste them together into a new Word (or equiv.) .doc file. Or work with the two files that is too much for you. If you have issues doing any of this, or whatever, send me your email address via a PM, and I will email the original file to you.
Here are the two parts of the the manual, combined, as a PDF.
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Couple of less fuzzy shots.
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The user manual v.1.1 of BG7TBL LCD GPSDO describes the editing of the LCD display. Someone knows which software to use? Has anyone tried it successfully?
Jörg
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Lady Heather has a built in simple terminal emulator that can be used. Heather also has the !u command that will send commands to the device... but that may not work since it automatically adds the checksum characters to NMEA messages (if the input command does not have a checksum). I don't know if BG8TBL's gate array tolerates the checksum in his custom message. I'm going to mod Heather to add a way of disabling the automatic checksum addition.
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Re. BG7TBL LCD-GPSDO:
Has anyone been able to send and execute a LCD command to this unit? I have been working on this and pulled a zero so far. Ted
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Re. Issue I have with programming the BG7TBL LCD-GPSDO:
I want to change the LCD to display time in EST, and the frequency as PPB offset,[/b] and the command for this is $GPGTC, 2 EST +0500t*. I can't get this to work, although this is exactly the same task as BG7TBL shows in his example on page 14 and 15 (the entry he used for the "www.fenjin.com Terminal program") in his Version 1.1 Instruction Manual. He used this example because I asked him if I had the command correct for doing this in a email I sent him. He then put in his new V 1.1 manual that he sent me, that I then posted here to share with everyone. How simple can it be(?). Of course I can send him another email, but I would prefer work this out first possible, due to the language barrier here between us. And it seems like the freeware Terminal Emulator 'Termite' would handle the task of doing this. Available here > https://www.compuphase.com/software_termite.htm (https://www.compuphase.com/software_termite.htm)
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While waiting for my unit to arrive, here is my understanding of the commands provided in the PDF file (thank you all for contacting the seller and getting it for us!). Please be aware that I might be completely wrong, so proceed with caution at your own risk! :)
Baud rate is 9600 BPS, 8N1, first you need to connect the DB9 connector and then short-circuit the test points on the main PCB, labeled as "O(pen): RUN, C(losed): TEST" in order to enter into TEST mode. Not sure if this should be done while the unit is powered on or before plugging in the power? And I think that you should power-cycle the unit when finished (received OK! in the terminal emulator).
All commands are sent as ASCII string, starting with "$GPGTC," followed by 12 bytes and ending with a "T*".
Valid/accepted command response is "OK!".
Command template is:
$GPGTC,X1 X2 X3 X4 X5 X6 X7 X8 X9 X10 X11 X12 T*
X1 controls the way frequency offset is being displayed, as follows:
0,10000000.0000Hz
1,10M +/-0.0000Hz
2,10M +/-000.00ppb
3,10M +/-0.00000ppm
X2-X7 is the string shown on the 1-st display line, after the GPS signal strength indicator
Timezone string to be displayed (i.e. UTC, EST, BST), I guess that the examples below include the actual 6 bytes, so the command is actually "__UTC_" as in "space, space, U, T, C, space" in order to complete the bytes.
X8 is the timezone offset
Valid values are "+" or "-"
X9 X10 is the timezone offset in hours
Valid values are "00" to "23"
X11 X12 is the timezone offset in minutes
Valid values are "00" to "59"
Examples:
1. Display BJT string as timezone identificator, actual timezone offset of UTC+0800, frequency in ppb (X1 byte == 2)
$GPGTC,2__BJT_+0800T*
2. Display GMT string, timezone offset of UTC+0000, frequency in 10000000.0000Hz (X1 byte == 0)
$GPGTC,0__GMT_+0000T*
3. Display EST string, UTC-0500, frequency in PPM (X1 byte == 3)
$GPGTC,3__EST_-0500T*
* All blank spaces are shown as underscores in the examples above
@ted572,
Can you try sending the command with an upper-case letter "T" at the end, as in $GPGTC,2 EST -0500T* (this is $GPGTC,__EST_-0500T*, replace underscores with blank spaces)?
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Re Post: Reply #576
Thank you for the reply, and if nothing else its nice to hear that someone else is interested in the LCD-GPSDO programming. I have this information in my constructed English only version of the manual, where I included text of the newer info from BG7TBL's V 1.1. I have worked this to death trying different quantities of spaces, etc. And as I said in a previous post, BG7TBL used my desired program commands in his "www.fenjin.com Terminal program" (P 14/15). So it should be easy. I'm a retired RF engineer, so this is not new to me, and I'm embarrassed to be having this issue.
There may be a timing requirement, such as - 'close the test point' and then 'immediately (or at least with minimum delay) send the command', but it seems unlikely. Although I haven't tried this yet. I will, but I just need a break from this. I have been ill and I'm still recovering, although having some relapses, so this has been physically taxing on me.
I sent the V 1.1 manual to a Chinese friend that is also a engineer, and ask him to look at page 14 and try to tell me what some of the labels are that I wasn't able to figure out myself. I did this because it kind of looks like he may have chosen to send the command $ (string) as ASCII, and if so, I don't understand. I even tried to find the Terminal program BG7TBL used, and of course nothing came up. Google is very limited in China as you probably know. I set-up another terminal program for sending my command $ as ASCII, and the program would always lock up due to a error condition. I didn't expect that, but I also didn't expect it to work.
t
Thanks for for interest and concern. And by the way if I hadn't known about this LCD display programming capability, I would have been very happy with this unit as is. But, now I want to see the GPS Calculated Freq. Offset in 'PPB'.
Cheers, Ted
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Hello Ted, in that case I am sorry to be posting information that is already known and tried.
And I am certainly interested in modifying the LCD-GPSDO display according to the instructions, but as I said my unit is at least 2 weeks out so I will have to wait a bit before being able to play with the terminal.
If I may ask - is it responding to any of the commands, do you receive any response at all from the unit when in TEST/PGM mode?
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Re. Post: Reply #578
Hello Istamov: It is nice to have another person interested in the LCD programming. Great. . . No, I haven't seen any response from the unit at all after sending a command to it. It sounds like the most we can expect is Ok, if it actually was. Although it would be nice if it replied with a syntax error, etc, if the command wasn't valid, In a couple of days or so after I hear from my Chinese friend, and I have @*&#'ed (tried again) around a little more with it, I will send a email to BG7TBL with our current status/questions. So if you have questions for him, please feel free to forward them to me, or of course you can send him a email yourself. Cheers, Ted
Edit: kj7e posted a very nice English version BG7TBL LCD-GPSDO Manual a couple of pages back.
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Some of their (crappy) examples show a ':' in the time zone offset (+05:00), others do not (+0500). Since they say the string is 12 chars long, I suspect you do not use the ':'
Whatever is correct, he totally screwed up that command. It is supposed to be NMEA formatted. Spaces are not allowed in NMEA commands. If there is an "*" in a NMEA command, it must be at the end and followed by a checksum. Also he is using $GPGTC as his proprietary command. All proprietary messages should begin with "$P".
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Success apparently at last, with programming Display Options of the LCD-GPSDO[/b] :)
For EST time and Freq. Offset in PPM, I used the command: $GPGTC,2 EST +0500T* Although to get it to work I found merely by accident that doubling the command will do it. I verified several different times that sending the single command wouldn't work for me. Although when I pasted the command into my Terminal Emulation program's TX Data Send Field twice, that it would work every time. As here: $GPGTC,2 EST +0000T*$ESTGTC,2 EST +0500T*
I decided that I didn't want to deal with Daylight Savings Time, so I chose use 'UTC Time and Frequency Offset in PPM'. And I used this command: $GPGTC,2 UTC +0000T* So of course I had to use the following: $GPGTC,2 UTC +0000T*$GPGTC,2 UPC +0000T* Oh, this is so, so nice!
Something unusual is caused if you put a ' -' in from of the numeric time offset value. Such as -0500 for EST. Then when the time in seconds goes up - such as 57, 58, 59, etc, - the time in minutes goes down (in reverse). i/e. from 30 minutes, down to 29 minutes. :-// I recommend NOT experimenting with this!
I did use the freeware Terminal Emulator 'Termite' https://www.compuphase.com/software_termite.htm (https://www.compuphase.com/software_termite.htm) Hey, maybe this caused some of these issues with having to send double commands in series, although unlikely, and it did the job.
News Flash ! No, this Terminal Emulator has not caused any issues, in fact it has proven to work very well, easy to setup, and use. Plus being Freeware, the price is right
Edit: I'm going to talk to (email actually) B7TBL about this the above before recommending that others try doing it.[/b]
Edit 2: I just noticed a +43 minute error/offset in UTC Time on my unit. I don't know what caused this, but I imagine that it is related to issuing a -0500, or -0000 command to it. I have asked BG7TBL about this. So please wait until I report back on this before you make any programming changes.
Issue Resolved: This issue was caused by using a command with -xx00 Time data in it as I suspected. Do NOT do this at home, or experiment with a command like this, as I did. My fault, although I was able to repair it with BG7TBL's assistance. All is Ok again.
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"Example Commands for changing the LCD Display Options on the BG7TBL LCD-GPSDO"
For the normal default display of 'UTC Time and Frequency Hz: $GPGTC,0 UTC +0000T*
Note: You would use this if you wanted to restore the default, from currently having a different Display enabled.
Note: These Display Command strings each require a single space before 'UTC', and a double (2 spaces)
after 'UTC'.
To Display 'UTC Time' and 'Freq. Error in PPB': $GPGTC,2 UTC +0000T*
To Display 'EST Time' and Freq. 'Error in PPB': $GPGTC,2 EST +0500T*
To Display 'EST Time' and Frequency in Hz: $GPGTC,0 EST +0500T*
Suggestion: Before using EST, or any other Time Zone that also uses Daylight Savings Time (DST) think about the consequences of possibly having to deal with DST. I initially wanted to use EST, and then decided to stay with UTC. And by the way you can also label it GMT if you want, just replace UTC with GMT in the command string.
My unit is working great and I especially enjoy having the capability for displaying Frequency Error in PPB.
FYI: 001.00, or 1 ppb is 1 part in 10 to -9 (0.01 Hz @ 10 MHz), and 000.01 is 1 part in 10 to -11 (0.000,1 Hz @ 10 MHz) may also be referred to as 10 parts in 10 to -12.
Here is a Programming Tip I discovered that I suggest you use: If you want to send a command to the GPSDO in one shot then send it twice in one string. So for example if you want to send $GPGTC,2 UTC +0000T* (remember to use the 1 and 2 spaces), send it as $GPGTC,2 UTC +0000T*$GPGTC,2 UTC +0000T* I informed BG7TBL about this, it works, and is Ok to use. This is not complicated, and if you want to program the LCD for a Optional Display format, you only have to do it once!
To program a GPSDO LCD Display Option: With the GPSDO's top cover removed, place a connection across the Test/Program Jumper located on the main PCB, just behind the Rear Panel's 3 LEDs. Send your command through the Rear Panel's RS232 connector. Remove the Test Jumper connection. Remove DC Power for a few seconds, reapply DC Power. Your GPSDO should boot up and display your new LCD format.
I use a 'USB to Serial Port (RS232) Cable/Adapter' between my PC and the GPSDO for Programing and Monitoring. Very inexpensive on eBay.
For Monitoring I prefer: VisualGPSView, freeware, http://www.visualgps.net/, (http://www.visualgps.net/,) very easy to setup, use, and to see the Satellite Signal Levels from a distance, and no magnifying glass is required.
For Programming I prefer: 'Termite' Terminal Emulator, freeware, https://www.compuphase.com/software_termite.htm, (https://www.compuphase.com/software_termite.htm,) very easy to use and setup, and it is a Portable Application that you just Run, as no installation is required (you can even run it from a USB Thumb Drive), and it works perfectly with this GPSDO. Configuration Settings for Termite: Port: A/R (press 'v' to see what is available), Baud rate-9600, Data bits-8, Stop bits-1, Parity-none, Flow control-none, Transmitted text-Append nothing, Receive text: Polling-500 ms, Max lines-25, Options: Stay on top, Quit on Escape, Automatic edit line, Keep history, Plugins-none
Enjoy the Optional LCD Display Options: The default display itself is great, so there is no reason to change, but we have the options thanks to BG7TBL.
Miscellaneous:
1. The potentiometer, RP1, on the Display Board is a Contrast adjustment for the LCD.
2. I configured my unit to supply 5 VDC to the GPS Antenna (vs. the default 3.3 VDC) because my Active GPS Antenna and In-line GPS Pre-Amp are both designed for 5 VDC operation. To do this move the SMT Fuse from 'ANT 3.3V', to 'ANT 5V' (these are clearly marked) on the bottom of the Main PCB next to the U-blox GPS Receiver IC.
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This video just popped up, in Polish, but shows startup to stabilization.
www.youtube.com/watch?v=1NFTsVPzD-w (https://www.youtube.com/watch?v=1NFTsVPzD-w)
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BG7TBL LCD-GPSDO - English translation of the Chinese/English User Manual with programming updates incorporated.
Also included separately, information on the BG7BL GPS Distribution Amplifier.
Please let me know (via PM, etc) if you have a question, or find errors.
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Hello. I have collected some statistical values with the BG7TBL LCD GPSDO.
I have unfortunately no RubidiumStandard for best stability measurement. My best reference is a HP 10544A OCXO. I think with a rubidium show up even slightly better stability over a comparable period of time. The absolute frequency is not to assess in this case. We will consider only the fluctuations over 1000-2000 seconds in a 19.5-20-5 ° C environment.
The Analyzer uses the GPSDO as an external reference. the HP OCXO is measured. Gate time always 1 second. This results in a reading per second. The amount of N corresponds to the measured time in seconds.
In the best case, it looks like this:
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In case of second best, it looks like this:
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In the so far worst case it looks like this:
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Besides the absolute frequency accuracy and drift measurements, are there any measurements/specifications concerning the phase noise?
I wonder if i ruin my e.g. spectrum analyzers measurement precision concerning phase noise when using an external GPSDO reference.
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I think what comes up also is jitter specification.
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GPS discipling an OCXO will keep the OCXO freq accurate at the expense of slightly worse phase noise than the OCXO's undisciplined values. The difference is usually not significant, particularly if the GPSDO OCXO does not have particularly low phase noise.
Some GPSDOs let you disable disciplining and hold the OCXO EFC voltage at a fixed value. This can be handy if you are multiplying the output freq into the microwave range. You trade off frequency accuracy/drift for phase noise. The OCXOs in most Thunderbolts have very low phase noise, but do have quite a bit of temperature sensitivity.
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KE5FX did measure the phase noise of a 2015 version BG7TBLGPSDO;
http://www.ke5fx.com/gpscomp.htm (http://www.ke5fx.com/gpscomp.htm)
It was noted the 1pps signal seemed to be degrading the phase noise performance some. No idea if this was just his sample or if there have been any improvements in later editions.
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Got mine yesterday. It is dated 2017-12-16 on the front. Clock TIE measured by MSOS804A.
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Now with an HP Z3805A GPSDO as an external reference, I have been able to repeat the review of the BG7TBL LCD GPSDO.
Both devices are in continuous operation for two weeks.
The up and down of the frequency behavior from my previous post, was a feature of the old HP OCXO 10544A.
The current review with the HP Z3805 as a reference shows a better result.
I have taken some samples over 10 hours to check the difference between both GPSDO.
The result from the last 24h test, can be seen below.
Compared to the HP Z3805, the BG7TBL is set in most of the time about 90 µhz to 140 µhz lower.
Which of the two devices is more accurate, i can`t say.
The setup of the Tektronix FCA 3000 (Pendulum/Spectracom CNT90/Fluke PM 6690) still has some surprises with a influence on the measurement result.
But later on.
The current settings:
Ext. Ref: HP Z 3805A
Gate Time: 1 sec., ARM: off
Smart frequency: off
Trigger: manual
Input: Ch. A, 50 ohm, 1x,
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Now my experience at the Tektronix FCA 3000 (Pendulum/Spectracom CNT90/Fluke PM 6690) show the somewhat confusing measurement results.
Gate time greater than 2.5 secs only works with the "smart Frequency" feature is enabled.
That's what the manufacturer writes.
"Smart frequency (valid only if the selected measurement function is frequency or period average)
By means of continuous timestamp and regression analysis, the resolution is increased for
Measuring times between 0.2 s and 100 S. "
By default, this function is on "auto". This means for all measurements with greater as 200 ms gate time, this function is "on ".
In my case, this function measures an error of about 700 µHz too low (@ 10 MHz). That measurement result is already somewhat averaged and in the statistical analysis the deviations are lower.
I'll show you two examples for comparison in the appendix. For a measurement result with better, absolute accuracy, smart frequency should probably be turned off.
When measuring results are posted by these devices, the information about this status is important.
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A few more experiments with the BG7TBL LCD GPSDO.
The setup as last time.
Refernce: HP Z3805A
Counter: Tek FCA3000
DUT: BG7TBL GPSDO 2017-12-16
This time, i set the GateTime to 10 seconds .
This makes it easier to assess the drift in the TimeDomane.
The observation period is about nine hours over the night.
What influence the BG7TBL GPSDO makes and which the HP Z3805A, I can`t yet say exactly.
At the moment I have no stable timbase without disciplining.
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Suddenly the "L" in the display of the GPSDO is missing again.
For about seven minutes, the 10 MHz in the LCD display jumps up and down about +/-0.016 Hz.
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After that, I recorded the stabilization of the GPSDO for a period of about five hours.
The device needs about two hours to stabilize itself to its frequency exactly as before.
This plot is created again with 10 seconds GateTime.
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Jorg,
Did you happen to have Lady Heather monitoring the GPS signals at the time the Lock "L" was lost? I would suspect a momentary signal strength issue.
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Hi kj7e. No, not this time.
But the signal strength indicator showed all the time 4-5 bars.
I have tried in the past time in LH and U Center to detect abnormalities. No result.
There was also no "no fix" message.
This effect happens occasionally and not for the first time.
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Power glitch maybe? I have not seen mine ever loose lock while powered on. I have pulled power momentarily now and then for various reasons. It will come right back without a "No Fix" message but will loose lock for a few min.
Running a test now to see how stable the hold over is. Going to run it with no antenna for a few days. I have a good record on the stability my HP 53132A Opt 010 to compare it to.
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In all the situations where the L is lost, I could no abnormalities which see on the power point. If I pull out the antenna plug, the display will immediately "GPS NO FIX". "
I can test a different PSU the next time time and let the results surprise me.
Due to recent events, I'm now a test recording without GPS antenna in the "GPS NO FIX" mode. "
The first 15 minutes point to a more stable 10 MHz signal. We'll see how it looks for several hours.
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I really don't like switch mode power adapters, so I built a compact dedicated 12v 3a LDO linear supply for the GPSDO and 10MHz distribution amp.
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First an example of the characteristic of the BG7TBL LCD GPSDO in hold over mode for about 12 hours.
Below is a plot and statistics in disciplined mode once again as a comparison.
Gate Time 10 Sek.
Reference for Frequency Counter: HP Z 3805A
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I found the same thing but ran mine for 48 hours in holdover. The Trimble 65256 oven used is seriously impressive and stable.
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<2E-10 over 12 hours? How did the 48 hour plots compare?
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<2E-10 over 12 hours? How did the 48 hour plots compare?
Inconclusive, I could not tell if my HP 53132A's 10811-60160 or the Trimble 65256 oven that was drifting. Started with about 800uHz difference then drifted up and down no more than 2mHz by 48 hours. I would need a second GPSDO to tie my counter to and run a much longer test, like as in 30 days.
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<2E-10 over 12 hours? How did the 48 hour plots compare?
I removed the GPS antenna again and started a new recording of the HoldOver mode for 48h or so.
I hope that there will be no EMC influences in the time.
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My 48 hour test was inconclusive by itself. Im running two 24 hour tests, first comparing the GPSDO with GPS lock to my counters internal reference, then I will repeat this with the GPSDO in free run. I suspect I wont see much difference as the Trimble oven used in the GPSDO seems to be very good indeed. I really need a Rubidum or a second GPSDO for a more stable ref on the counter for this, but thats how good the Trimble oven seems to be.
GPSDO locked, HP 53132 with HP Option 010 HS oven with the following settings;
Gate set to 11 digits (34.4sec gate time), 2512 measurements comes to almost exactly 24 hours. The LSD is solid and stable when the Gate is set by Digit vs Time.
STD DEV;
(https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/?action=dlattach;attach=412925;image)
MEAN;
(https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/?action=dlattach;attach=412927;image)
MAX;
(https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/?action=dlattach;attach=412929;image)
MIN;
(https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/?action=dlattach;attach=412931;image)
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Same as above but with the GPSDO in Free Run or Hold Over with no GPS signal;
STD DEV;
(https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/?action=dlattach;attach=413275;image)
MEAN;
(https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/?action=dlattach;attach=413277;image)
MAX;
(https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/?action=dlattach;attach=413279;image)
MIN;
(https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/?action=dlattach;attach=413281;image)
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<2E-10 over 12 hours? How did the 48 hour plots compare?
Now another flood of images of the "Free run mode " of the BG7TBL LCD GPSDO without a GPS signal.
Measuring conditions. Tek FCA3000 with HP Z3805A as an external time-base.
Gate-time 10 sec. Ambient temperature min. 18 °c/max 22 °c.
From top to bottom after 12h, 24h, 36h, 48h and current 60h.
I'm going to keep the record running for about two days.
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And here's the rest.
Current modification: 22.4.18
I have added the recording at a duration of 120 h Hold Ovr Mode .
I think you can now estimate the drift well if you construct a regression line over the plot.
On the Y axis are 1mHz/div. On the x axis about 13, 5h/div in this view.
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Hello Jörg
Nice to see all your measurements. Especially the long term.
Seems that your BG7TBL GPSDO is better in hold than in run ;)
In your reply #596 April 13 you lost "locked" and my guess would be that the OCXO made a jump of a few tenths of a ppb. I have seen jumps after days, after months and even more frequent on my OCXO's bought from eBay. I have one MV102 OCXO that is so bad that I don't get a useful ADEV graph between jumps. Of course I have some OCXO that I haven't seen a jump on (maybe have run them to little :) )
What is more interesting with your graph is the step wise frequency changes. For me it seems that the BG7TBL GPSDO you have has an FLL. Like the first BG7TBL GPSDO's. So it counts the frequency for about a minute and when corrects. If the error gets smaller it counts longer and make smaller steps. As has been pointed out earlier in the thread and by KE5FX tests, FLL is not the optimum for a GPSDO. This is also the reason you even after 40000seconds averaging has only about 10 digits accuracy.
Even a very simple GPSDO like mine (https://www.eevblog.com/forum/projects/lars-diy-gpsdo-with-arduino-and-1ns-resolution-tic/?all (https://www.eevblog.com/forum/projects/lars-diy-gpsdo-with-arduino-and-1ns-resolution-tic/?all) )
has a integral term that normally hold the output phase within 20-50ns (even with a DOT050V TCXO!). 40ns in 40000second should be 1E-12 so 12 digits.
Making a PI-loop is not difficult. A brief explanation is on page 8 in my instruction. On page 15 I have several good links to GPSDO control loops also. But it seems BG7TBL hasn't tried for several years.
Another thought is why nobody (except KE5FX) do time interval measurements between the BG7TBL and other professional GPSDO's with their excellent counters. I really like timelab by KE5FX. Also if the 1PPS comes from the GPS module and not is a divided down 10MHz it would be interesting to see if the phase (time) goes away. 0.1ppb would be 4us in 40000seconds. If I remember correct KE5FX showed this.
Lars
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I was monitoring two Trimble UMMC units on a scope and they are locked in phase. Every so many hours, the signals relative phase would start to drift to +/- one cycle and then be locked again. The cycle repeats... Maybe in HO they will be stable enough for me to identify which one it is...
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Hello Lars. Your guess is quite possible.
The user DajMasta has also shown interesting records of 2016-05-31 model in his post «Reply #448 on: September 15, 2017, 04:32:27 pm».
In comparison, the BG7TBL LCD model 2017 has resulted in a change.
I could only observe these jumps of the output frequency in situations where the letter "L " disappeared from the display. Not in "GPS no fixed " mode or in "normal" modes.
I have also added a 144h HoldOverMode plot to my post «Reply #611 on: April 20, 2018, 03:42:36 AM».
I think you can now estimate the drift well if you construct a regression line over the plot.
On the Y axis are 1mHz/div. On the x axis about 13, 5h/div in this view.
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Hello kj7e.
I think your option 10 time base is not bad.
In a period of 12-24h you can use the option to exclude the effects of disciplining on the counter reference.
For example, at the moment I cannot tell exactly whether the HP Z3805A GPSDO or the BG7TBL GPSDO is responsible for medium-term fluctuations when both are in the GPS lock.
Can you visualize the data from your HP 53132A on the PC via the GPIB interface?
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Hello kj7e.
I think your option 10 time base is not bad.
In a period of 12-24h you can use the option to exclude the effects of disciplining on the counter reference.
For example, at the moment I cannot tell exactly whether the HP Z3805A GPSDO or the BG7TBL GPSDO is responsible for medium-term fluctuations when both are in the GPS lock.
Can you visualize the data from your HP 53132A on the PC via the GPIB interface?
Working on that, I have an NI GPIB to Ethernet adapter on the way.
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Hello Jörg,
I am still not impressed by reply 448 saying the algorithm is changed. Could still be a FLL that depending on OCXO drift gives your 10 digits or in DajMastas case 11 digits over the 12 hours.
KE5FX already long ago got information that the resolution of the DAC were in the 1E-11 range so the strange behaviour reported doesn't convince me it is any better algorithms. If someone can show me that the 10Mhz stays within 100ns for 12 hours compared to a good GPSDO as other professional GPSDO's does it would be good.
Even without regression I should say the drift of your OCXO is about -2E-11 per day that is very good.
Lars
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Hello Lars. I have measured the phase and time interval of the BG7TL GPSDO (input B) against the professional hp Z 3805A GPSDO (input A).
In this view, the requires phase is approximately 16 min 30 sec for a run of 0 degrees to 0 degrees. At TI measurement it is about 20 min 10 sec for a complete run from 0 to 0 ns. Input B was measured relative to input A. Both GPSDO are in GPS lock mode. For the use with the scope I have only one old analogue oscilloscopes available.
This is not so comfortable for automated measuring like a DSO
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Hello Jörg,
and thanks for doing the time interval measurements. I don't think you need a DSO for this measurement as you have such an excellent instrument for time interval.
As the frequency of both sources are very close to 10MHz the period time is very close to 100ns. So both your measurements wraps at 100ns drift. Normally two locked GPSDO's will drift back and forth about 20-50ns but here one drifts away all the time
16min 30s is 990secs and 100ns during 990secs shows an offset of about 100ns/990s that is about 1E-10. 100ns in 20min and 10sec is 1210 secs so 100ns/1210s is about 8E-11. So the frequency varies a little between the measurements. What concerns me is that one of the locked GPSDO continuously drift against the other. Sorry to say I guess it is the BG7TBL that still has the inferior FLL algoritm to steer the frequency.
Lars
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I could now mount a well GPS antenna in an exposed place.
Compared to the antenna outside the window, the stability of the navigation has improved considerably.
I could not determine a measurable change in the 10 MHz output from the BG7TBL LCD GPSDO.
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Of the units listed in the OP, which would be the most desirable?
Are any much better than the others?
I'm looking for a GPSDO and really don't know much about them.
Would these BG7TBL units be considered the best bang for the buck or should I look elsewhere for a ready to go box.
I'm very happy with this unit. I did the management mode and not had a single problem with my unit. I also added the 10mhz square wave output.
The existing units have the Star Management mode already completed.
https://www.ebay.com/itm/10Mhz-GPSDO-OSCILLOQUARTZ-OSA-OEM-GPS-GPSDO-10MHz-1PPS-STAR-GPS-Clock/262861459973?hash=item3d33c39205:g:sbYAAOSwh2xYAjrp (https://www.ebay.com/itm/10Mhz-GPSDO-OSCILLOQUARTZ-OSA-OEM-GPS-GPSDO-10MHz-1PPS-STAR-GPS-Clock/262861459973?hash=item3d33c39205:g:sbYAAOSwh2xYAjrp)
Do you need to mod these before you get any output? I have just bought one and the vendor claims it works with Lady Heather whilst mine shows no signs of communicating at all over RS232. Pin 2 is permanently at logic 1 (-5.8V) and pin 3 is at around zero volts. Pin 8 has the 1PPS ok. The unit as a whole seems to work ok (locks on to 10MHz as checked against a radio standard).
EDIT : Problem now fixed thanks to help from texaspyro.
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How does one control whether the output is a 10Mhz Square or Sine wave (or is it hard-wired one or the other)
The Manual just says that it is either a sine or a square wave -- it gives no other information...
Thanks!
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Would anyone know a good way to take the data coming into the GPSDO and export it into a data collection sheet like excel?
Thanks!
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@ian,
Default is a sine wave, I dont see a way to output a 10MHz square wave. If there is, its likely a PCB jumper on the bottom of the board.
@Brandon,
LadyHeather has logging functions that may work for you;
http://www.ke5fx.com/heather/readme.htm (http://www.ke5fx.com/heather/readme.htm)
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I plan on using the BG7TBL LCD-GPSDO for my setup. Would Lady Heather be compatible with it or does anyone have experience using that software with the BG7TBL LCD-GPSDO.
Thanks
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Yes, LadyHeather works very well here.
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Folks,
I have a BG7TBL 2015-09-17 with the oscilloquartz OCXO & U-Blox GPS. I was able to have this one evaluated when I got it and it was surprisingly stable and accurate.
I'd like to find another one like this for my 2nd radio but this BG7TBL version isn't available as a couple years back. I need the 10MHz for calibrating my Ham Radio stability and the GPS via RS-232 keeps my computer synced using NMEATime. There's now a few more modern versions of this GPSDO but I have no idea if they are unreliable junk or worth buying.
I'd appreciate opinions on what is current, offers what I need and is relatively inexpensive. I'll be more than happy with another BG7TBL if it's as good as the one I have but anything trustworthy will be fine.
Thanks.
Gary
KA1J
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https://www.ebay.com/itm/10Mhz-GPSDO-OSCILLOQUARTZ-OSA-OEM-GPS-GPSDO-10MHz-1PPS-STAR-GPS-Clock/262861459973?hash=item3d33c39205%3Ag%3AsbYAAOSwh2xYAjrp&_sacat=0&_nkw=osclloquartz+gpsdo&_from=R40&rt=nc&_trksid=m570.l1313 (https://www.ebay.com/itm/10Mhz-GPSDO-OSCILLOQUARTZ-OSA-OEM-GPS-GPSDO-10MHz-1PPS-STAR-GPS-Clock/262861459973?hash=item3d33c39205%3Ag%3AsbYAAOSwh2xYAjrp&_sacat=0&_nkw=osclloquartz+gpsdo&_from=R40&rt=nc&_trksid=m570.l1313)
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https://www.ebay.com/itm/10Mhz-GPSDO-OSCILLOQUARTZ-OSA-OEM-GPS-GPSDO-10MHz-1PPS-STAR-GPS-Clock/262861459973?hash=item3d33c39205%3Ag%3AsbYAAOSwh2xYAjrp&_sacat=0&_nkw=osclloquartz+gpsdo&_from=R40&rt=nc&_trksid=m570.l1313 (https://www.ebay.com/itm/10Mhz-GPSDO-OSCILLOQUARTZ-OSA-OEM-GPS-GPSDO-10MHz-1PPS-STAR-GPS-Clock/262861459973?hash=item3d33c39205%3Ag%3AsbYAAOSwh2xYAjrp&_sacat=0&_nkw=osclloquartz+gpsdo&_from=R40&rt=nc&_trksid=m570.l1313)
Thanks so much for that link, Texas. That looks to be much of what my BG7TBL is. It doesn't come with an antenna but that won't cost much. The HP readouts looked fine but on the photo of the readout from Lady Heather it reads:
ATDC: in 2358 secs
Holdover Perf Poor.
I'm not sure how to interpret the ATDC finding or a poor Holdover performance. Maybe it is inconsequential?
Thoughts?
And thanks again.
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It needs at least 24 hours or so of data to calculate the holdover compensation. Until then, it says "poor".
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It needs at least 24 hours or so of data to calculate the holdover compensation. Until then, it says "poor".
Thank you.
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Another version which has not had pics taken yet 2017-10-09.
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https://www.ebay.com/itm/10Mhz-GPSDO-OSCILLOQUARTZ-OSA-OEM-GPS-GPSDO-10MHz-1PPS-STAR-GPS-Clock/262861459973?hash=item3d33c39205%3Ag%3AsbYAAOSwh2xYAjrp&_sacat=0&_nkw=osclloquartz+gpsdo&_from=R40&rt=nc&_trksid=m570.l1313 (https://www.ebay.com/itm/10Mhz-GPSDO-OSCILLOQUARTZ-OSA-OEM-GPS-GPSDO-10MHz-1PPS-STAR-GPS-Clock/262861459973?hash=item3d33c39205%3Ag%3AsbYAAOSwh2xYAjrp&_sacat=0&_nkw=osclloquartz+gpsdo&_from=R40&rt=nc&_trksid=m570.l1313)
I just bought one of these units and it looks to be real nice. The lock time is reasonably quick. I'm still trying to decipher what the "ACT" LED is telling me. Any insight?
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I was wondering the same thing. Also, it's very dark during operation. Other than that, it's a great unit. I had mine for almost a year. No issue.
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I don't know what he has connected to the ACT LED, but attached is the Star4 ATDC manual.
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I don't know what he has connected to the ACT LED, but attached is the Star4 ATDC manual.
I took the liberty of contacting the seller (amoj1010) directly and queried him about the ACT LED. His reply, quoted, follows:
"when gps locked the act led is lighting always。 when gps try to locking ，it is Blink"
Filed for future reference. ::)
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Question for Texaspyro:
Is it possible to create a list of OSA STAR 4+ specific parameters that are active on Lady Heather? And those which can be set by keyboard commands?
A lot of them (Heather listing) seem inoperable.
I see my temperature log making jumps of approximately 2 oC in a seemingly random manner.
Thanks in advance & regards
Frans
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Most of the commands that set things are in the "P" menu. The "&" menu has a command or two for setting some disciplining parameters.
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This answer is not very specific.
And quite difficult to find any explanations about the functionality of both ways.
I read the various Time-Nuts discussions on these subjects and found no clear, specific and itemised explanations (2015 - 2018).
Probably I have to find this out myself from the source code and the subject manuals.
Would have been nice to have the correct specifications. I see however that to compose something like this is quite a task.
Frans
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A special version of BG7TBL gpsdo which outputs 44.1khz square wave.
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A special version of BG7TBL gpsdo which outputs 44.1khz square wave.
A PLL board solder on the OCXO. AK8133E and ALTERA PLD on the PLL board.
The output trace is cut by removing 2 resistors, 1 inductor and 1 capacitor.
I want to restore it to output 1 PPS and 10MHz. I have soldered 2 150ohm resistors on the 1PPS trace and it works fine. But what value of inductor and capacitor should I choose to restore the 10MHz output BPF?
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BG7TBL LCD-GPSDO English Manual
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Recently, a GPSDO based on the Oscilloquartz Star 4 + arrived. I have had great hope for good precision and stability.
Comparing with my HP Z 3805A, the precision of the 10 MHz output is very good. Slightly more accurate than the BG7TBL 2017-12-16 GPSDO.
I'm a bit unhappy with frequency stability. When the OSA Star4 is in GPS mode, the frequency jumps about +/-2 mHz around the 10 MHz.
Going the unit into the hold over mode, stability is at the expected level.
Jörg
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I've not performed this experiment on my Star 4+ - I will probably try comparing it to one of my two working Rubidiums but I can't do that until I get my lab back together properly.
In the interim, a quick question, how long had the Star 4+ been running? I wonder if it was still conducting a self-survey or if its algorithms have bigger changes initially and reduce them over time.
Can you leave it running for 24 hours and see if you still get the same fluctuations?
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HI jpb. At the time I took the pictures, the unit was about 30 h online.
The ATDC is already active, which only happens after 24h of calculation time. The frequency of 10 MHz +/-2mHz always jumps.
Regards. Jörg
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HI jpb. At the time I took the pictures, the unit was about 30 h online.
The ATDC is already active, which only happens after 24h of calculation time. The frequency of 10 MHz +/-2mHz always jumps.
Regards. Jörg
Thank you Jörg.
I'll have to check mine when I get the chance. I only checked mine over long gates where its average frequency is very good. If these jumps are a feature then perhaps we need to phase lock a second OCXO to it with a loop time constant of 100 seconds or so.
Looking at your plots, it looks as if it is the result of the LSB of the DAC controlling the OCXO - but doing a quick calculation:
the tuning on the 8663 is 0.3 ppm over 10V (according to the datasheet). 2mHz is 2 x 10^-3/10^7 = 2 x 10^-10
2 x 10^-10/3x10^-7 = 1/1,500 which is only about 11 bits, while I'd assume at least 16bit DAC which should give a resolution of under 50 microHertz so it can't be a resolution thing (unless they only use around 11 bits!)
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HI jpb. I also did the review with 10 sec avg time. The Allan Dev is as poor as at 1 sec avg.
Right now I'm taking a test with 100 sec. This looks better but about 2-3 X worse
as a BG7TBL 2017-12-16 GPSDO at 1 sec measuring time.
The manual of the OSA Star4 shows, that the PLL time constant can be varied.
Maybe that can make a better behavior of the 10 MHz output.
In Lady Heather's, I couldn't see the command.
Greeting. Jörg
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In Lady Heather's, I couldn't see the command.
&t
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HI jpb. I also did the review with 10 sec avg time. The Allan Dev is as poor as at 1 sec avg.
Right now I'm taking a test with 100 sec. This looks better but about 2-3 X worse
as a BG7TBL 2017-12-16 GPSDO at 1 sec measuring time.
The manual of the OSA Star4 shows, that the PLL time constant can be varied.
Maybe that can make a better behavior of the 10 MHz output.
In Lady Heather's, I couldn't see the command.
Greeting. Jörg
I am very interested in the manual of the OSA Star4.
Any suggestions where?
My GPSDO is exactly the same and quite satisfactory.
However, lack of a manual restricts my options and understanding.
Sofar, looking for a manual was fruitless.
Thanks in advance,
Frans
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HI jpb. I also did the review with 10 sec avg time. The Allan Dev is as poor as at 1 sec avg.
Right now I'm taking a test with 100 sec. This looks better but about 2-3 X worse
as a BG7TBL 2017-12-16 GPSDO at 1 sec measuring time.
The manual of the OSA Star4 shows, that the PLL time constant can be varied.
Maybe that can make a better behavior of the 10 MHz output.
In Lady Heather's, I couldn't see the command.
Greeting. Jörg
I am very interested in the manual of the OSA Star4.
Any suggestions where?
My GPSDO is exactly the same and quite satisfactory.
However, lack of a manual restricts my options and understanding.
Sofar, looking for a manual was fruitless.
Thanks in advance,
Frans
Yes, I too would like to get hold of the manual. I did a quick search yesterday but couldn't find it on line.
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Try this...
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Try this...
Thank you.
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Hello, thanks to texaspyro for pointing out with "&t". That was very helpful.
The PLL time constant was 200 seconds. I adjusted the TC to 5000 seconds. Now the short-term stability is more determined by the OCXO and at the level of the BG7TBL 2017-12-16 GPSDO. The BG7TBL GPSDO is about 700-1000 μHz lower in frequency compared to my HP Z 3805A.
The OSA Star4 shows very nice close to the HP GPSDO.
Here is an example with 10 sec avg time over 12 hours.
HP Z 3805A as an external reference and OSA Star4+ on input B of the TEK FCA3000.
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A good message for all people who can't mount a Timig GPS antenna at an optimal place.
I took comparison measurements of an antenna on the roof and one on the outside of the window.
I could not notice a significant difference in 10 MHz accuracy, short-term stability or drift.
Both measurements are with the HP Z3805A as ext. reference, and the Oscilloquartz Star4+ GPSDO on Input B to the counter.
Gate Time is 1 second in a 12-hour period. In both measurements, the Star4 unit had completely finished the setup on the antenna.
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I think there is a need to have phase correlation as well...
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Of course. I only checked the 10 MHz output. Many people just need an accurate, stable reference for the frequency, without much technical effort.
For the most accurate 1PPS output in a synchronized environment, a more optimal setup can be the more accurate solution.
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About 2 weeks ago my 2017-12 LCD BG7TBL GPSDO would no longer lock, the supplied Trimble 65256 OCXO aged out and is now beyond the VFC range, slowly drifting down. I have another 65256 OCXO on order.
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Thats too soon! That really sucks.
About 2 weeks ago my 2017-12 LCD BG7TBL GPSDO would no longer lock, the supplied Trimble 65256 OCXO aged out and is now beyond the VFC range, slowly drifting down. I have another 65256 OCXO on order.
This reminds me that I should likely buy at least one, maybe two of the OCXO that my GPSDO came with.
(But I suppose that if they have been removed from service they might be on their last legs too).
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^ I think I just got a bit unlucky, I suspect most samples will run for years and stay in tolerance. I'm going to play with a few OCXO's, also have an OSCILLOQUARTZ 8663-XS on the way.
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Has anyone tried and been successful adding a LCD to the non LCD version? Mine has the socket installed for the ribbon cable.
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Jorg,
You would likely do better if you put a ground plane (even something as small as a CD/DVD) underneath your puck antenna.
They are designed to use one. Any flat piece of steel works well because of the magnet.
I'm surprised people do as well as they have because most ceramic patch antennas are just the top part of the antenna, the ground plane thats supposed to go underneath (say the roof of a car) is the bottom part. The puck antennas that are sold have a small ground plane but its intended to capacitively couple to a larger piece of metal.
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Just a quick update, replaced the original Trimble 65256 OCXO with a China sourced used 65256, the original was at the VFC DAC upper limit of 4.9v. The replacement is sitting at ~2.3v so seems there is plenty of life in the replacement part.
One interesting thing I noticed, even though the 65256 is spec'd for 12v Vcc its being fed a regulated 5v. There is a 0 ohm resistor that can be moved to feed it 12v from the input power, but I noticed no difference in performance of the OCXO running from either 5 or 12v other than initial oven warm up power. Perhaps the thinking here is a regulated 5v to the oven will provide slightly more stable oven regulation, so I left it as such.
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Hello cdev.
It is not always what it seems. The material under the puck antenna is powder coated aluminum.
So i had to fix the antenna for the experiment. Because it was just an experiment.
I could allow myself a temporary solution.
Of course, with the roof antenna, the quality and quantity of the GPS reception is much better. Since I am not dependent on the patch antenna.
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Just a quick update, replaced the original Trimble 65256 OCXO with a China sourced used 65256, the original was at the VFC DAC upper limit of 4.9v. The replacement is sitting at ~2.3v so seems there is plenty of life in the replacement part.
One interesting thing I noticed, even though the 65256 is spec'd for 12v Vcc its being fed a regulated 5v. There is a 0 ohm resistor that can be moved to feed it 12v from the input power, but I noticed no difference in performance of the OCXO running from either 5 or 12v other than initial oven warm up power. Perhaps the thinking here is a regulated 5v to the oven will provide slightly more stable oven regulation, so I left it as such.
There seems to be some confusion on the voltage rating for the 65256. I tested mine and found that the output reaches maximum amplitude with a supply voltage of ~4V. If it was rated for 12V, that wouldn't happen. You wouldn't reach maximum amplitude until maybe 8V-10V. I've also heard of people frying the 65256 by applying 12V. I suspect that the 0 ohm jumper is to allow for either a 5V or 12V oscillator on the same board.
Ed
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There seems to be some confusion on the voltage rating for the 65256. ...
Indeed, most everywhere you search on the internet Vcc is spec'd at 12v, but I suspect 5v is more likely. After about a full day of operation, the new 65256 VFC has been extremely steady (<1mv deviation seen for 48 hours after the first 24 hour period) and right about center of the DAC range. So it appears I got a bit lucky with the used replacement part.
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There seems to be some confusion on the voltage rating for the 65256. ...
The bare board runs on 6V (the Samsung version wants 5.5V). There are some packaged up devices that use a 12V (or possibly other) voltage input.
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Hi Texaspyro,
you mentioned a while ago that you'd add the Samsung variant to Lady Heather - have you had a chance to do this yet?
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Hi Texaspyro,
you mentioned a while ago that you'd add the Samsung variant to Lady Heather - have you had a chance to do this yet?
Yes, it works well. I hope to get the next release out in a (yeah, right) few days.
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I like the Lady Heather signal strength (or rather Signal to Noise) plot.
I've not really thought about it before, but I'm quite surprised by the magnitude (and roundness) of the black hole presumably over the north pole where GPS satellites don't go.
(I assume that this is the cause of the large black circle in the plot - there are houses/trees around blocking things but that is true in all directions.)
Unfortunately I have to mount my antenna on the north side of the house (where my study/lab is) so the black hole removes much of the sky. (My antenna is mounted on the top of my garden fence a little way from the house and also from neighbouring houes.)
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I just found this forum, and Im in the process of deciding whether or not to purchase the BG7TBL GPSDO. My intent is to use it in conjunction with my Flex 6500 SDR transceiver. I am realizing that there are several versions of this basic design. I'd like to have both 10 mhz both Sine ans Square wave output in addition to the 1PPS. I've seen a few units with a display of the NEMA info. Wondering if anyone can give me the following info:
1. What is the latest version and who is selling it?
2. Does anyone have any info on a Raspberry PI or Arduino display panel that would display the NEMA data?
3. Can NEMATime Panel be used stand alone, w/o taking control of your PC's time clock?
4. Seen some comments that one versions GPS recdeiver is much more sensitive than the other - truth?
Thanks
Bob, WA2SQQ
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Hi
since weeks I play arround with the FE-5680A but how you wanna change the frequency or the vfc ?
my question is how I can change the accuracy of the FE-5680A. All I found is change the temperature of the lamp.
How you wanna do that ?
pls make pictures if possible
Iam very interested in it. I have the same config, and a few FE-5680A bit just a HP 53131A with 10 digits.
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I took one of those GPSDO's with the LCD and combined it with a Extron distribution amplifiers. I did not like having two separate pieces taking up space.
All I had to do was change all the 75 ohm resistors in the amp to 50 ohm & add a pwr supply.
(https://farm1.staticflickr.com/944/42210160241_293446cf64_b.jpg) (https://flic.kr/p/27iY74t)P1010142 (2) (https://flic.kr/p/27iY74t)
(https://farm1.staticflickr.com/830/42210160531_4c2144e9ef_b.jpg) (https://flic.kr/p/27iY79t)P1010140 (2) (https://flic.kr/p/27iY79t)
(https://farm1.staticflickr.com/981/42210160651_90a04b556a_b.jpg) (https://flic.kr/p/27iY7bx)P1010139 (2) (https://flic.kr/p/27iY7bx)
(https://farm1.staticflickr.com/974/42210160391_0c5736eae8_b.jpg) (https://flic.kr/p/27iY774)P1010141 (2) (https://flic.kr/p/27iY774)
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Made a little how to video on changing out the normally supplied Trimble 65256 OCXO for an Oscilloquartz 8663-XS on my Dec 2017 LCD version. Just have to move the Vcc jumper from 5v to the 12 volt position and increase the EFC gain to 2x. The DAC for the EFC is 0-3.3v feeding one side of an LM358 with a default gain of 1.5 for 0-4.95v, 2x gives 0-6.6v and there is a 3x jumper for 0-9.9v as well. There is a guy selling NOS UCT 108663-01 OCXO's on eBay right now for cheap, which appear to be rebranded Oscilloquartz 8663-XS's.
https://www.ebay.com/itm/UCT-OSA-MY-108663-01-10MHz-12V-Double-Oven-OCXO-Crystal-Oscillator/264230742882 (https://www.ebay.com/itm/UCT-OSA-MY-108663-01-10MHz-12V-Double-Oven-OCXO-Crystal-Oscillator/264230742882)
More discussion on the UCT 108663 ocxo's can be found here: https://www.eevblog.com/forum/metrology/ocxo-calibration/msg1303548/#msg1303548 (https://www.eevblog.com/forum/metrology/ocxo-calibration/msg1303548/#msg1303548)
And here: https://www.eevblog.com/forum/testgear/purchasing-newer-vs-older-oxcos-for-gpsdo-use-pros-and-cons/ (https://www.eevblog.com/forum/testgear/purchasing-newer-vs-older-oxcos-for-gpsdo-use-pros-and-cons/)
Oscilloquartz 8663 datasheet: http://www.sungwhatech.com/product/pdf/aging/8663.pdf (http://www.sungwhatech.com/product/pdf/aging/8663.pdf)
https://youtu.be/gBkRFT9TgQI (https://youtu.be/gBkRFT9TgQI)
Testing some of the UCT 10866 ovens;
(https://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/IMG_8570.jpg) (https://s241.photobucket.com/user/wsmc551/media/Elecronics/IMG_8570.jpg.html)
UCT 10866 oven installed;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/IMG_8572.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/IMG_8572.jpg.html)
Bottom of the board with the UCT 10866 installed, set for 12v and 2x gain for the EFC;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/IMG_8574.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/IMG_8574.jpg.html)
As a side note, I also installed one of the UCT ovens in my BG7TBL 10MHz distribution amp, it also had provisions on the board to utilize the ovens Vref for the EFC trimmer. I've been very impressed with how little the UCT part drifts.
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Did you forget links ?
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Just going to add this here since there is very little info on this site elsewhere regarding the BG7TBL 10Mhz distribution Amp and I use it in conjunction with the GPSDO. Originally, mine was supplied with the DAPU 055F-ASDD OCXO, which was very drifty. I changed it out the DAPU oven for a Trimble 49422 which was a huge improvement, but the EFC Vref was sourced from an onboard voltage regulator and not the most stable. Recently I replaced the Trimble OCXO for a UCT 108663 so I could use the internal ovenized Vref for the EFC, just need to move R34 to the R35 pad. The UCT's Vref is very stable being ovenized, further increasing overall stability.
BG7TBL 10MHz distribution amp with the UCT OCXO;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/a.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/a.jpg.html)
Bottom;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/b.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/b.jpg.html)
EFC Vref source selection, move the 18 Ohm resistor from R34 pads (onboard) to R35 pads (OCXO);
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/c.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/c.jpg.html)
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Hi Guys,
I also got one of the STAR4 GPSDOs via eBay.
https://www.ebay.com/itm/Oscilloquartz-Star-4-GPS-Empfanger-10MHz-1PPS-GPS-disziplinierte-Uhr-GPSDO/292905940612 (https://www.ebay.com/itm/Oscilloquartz-Star-4-GPS-Empfanger-10MHz-1PPS-GPS-disziplinierte-Uhr-GPSDO/292905940612)
I found out that the sine output of the GPSDO is quite distorted and noisy and has a large DC offset, so I opened the unit and probed the OCXO directly with my 'scope. The OCXO signal looks good and has no offset, so I think there must be something wrong with this daughter board. Perhaps I will make my own one with an integrated distributor.
I measured a few of the signals on the 26pin connector and found out that the 10 MHz sine signal is missing, it is only available on the coaxial connector. Is that correct, or did this eBay seller modify other things on the STAR4 board, besides changing the coax connectors?
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Hey all, I have been following this thread for weeks and just ordered a unit for my radios...
https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/112700839490 (https://www.ebay.com/itm/Latest-10MHZ-SINE-WAVE-Sinewave-GPS-DISCiPLINED-CLOCK-GPSDO-with-LCD-Display/112700839490)
I was expecting to open it up and quickly identify the components so that I could make some tweaks if needed... A surprise for me with both the Crystal and GPS unlabeled. Any idea based on packaging what they are?
Thanks!
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Looks like the standard Trimble 65256 OCXO, which are very good.
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@Dwaynej
Kindly post some more photos of the top and bottom of the board, there are some changes I see, like the chip in front of the OCXO. I would like to look at the 2018 version you have closer.
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Incoming...
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More... Note the board SN 2019-01-07.
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More...
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Last pics... Note the L (for Locked?) on the display after running for a number of hours. Also, black plug is where ribbon cable plugs into main board to display board.
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Hi Guys,
I also got one of the STAR4 GPSDOs via eBay.
https://www.ebay.com/itm/Oscilloquartz-Star-4-GPS-Empfanger-10MHz-1PPS-GPS-disziplinierte-Uhr-GPSDO/292905940612 (https://www.ebay.com/itm/Oscilloquartz-Star-4-GPS-Empfanger-10MHz-1PPS-GPS-disziplinierte-Uhr-GPSDO/292905940612)
I found out that the sine output of the GPSDO is quite distorted and noisy and has a large DC offset, so I opened the unit and probed the OCXO directly with my 'scope. The OCXO signal looks good and has no offset, so I think there must be something wrong with this daughter board. Perhaps I will make my own one with an integrated distributor.
I measured a few of the signals on the 26pin connector and found out that the 10 MHz sine signal is missing, it is only available on the coaxial connector. Is that correct, or did this eBay seller modify other things on the STAR4 board, besides changing the coax connectors?
I get this with the tap for the square wave. Terminated to 50ohms....
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I just installed a BG7TBL. Thanks to everyone on this thread for helping me get up to starting speed.
FWIW, I found that simply putting the puck antenna on a baking sheet pan the SNR of the satellites nearly immediately (30 seconds or less?) jumped across the 14 satellites reporting SNRs an average of about 10dB per satellite. In two cases the difference was negative and in two cases there was no difference; in the other 10 the improvement was significant . The numbers represent a rapid capture of the new SNRs so it's possible the other four satellites might dial-in better if I take some more looks. This was just very fast, first impression but in one case a SNR increased 35dB and another increased 28dB. Long story short, just giving the magnetic puck antenna a ground plane is worth a try.
The LCD on the GPSDO is reporting 1,000,000.0012 Hz after about an hour - but that might have taken less if I had stared with the pan as a back plane.
The only thing I can't quite figure out is why the Lady Heather program doesn't render the satellite graphics without hitting Z and then some of the commands. I don't know why I can't get the standard view that everyone shows with the text/number info, the clock, and the satellite views to render all on one screen. Might be something to do with my graphic settings?
Thanks again to all the EEVers who have pioneered this stuff and shared your findings. EF
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An update. When I first looked at the Relative strength vs azimuth without the pan ground plane it looked like a very narrow view - maybe 60 degrees or less (I just remember it was narrow). With the pan ground plane it looks like I can see either the full 360 degrees or maybe I'm missing a few spots that might total up to about 60 degrees. I'm still trying to interpret what I'm seeing. This is kind of fun. :)
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Another update. While I was connecting the GPSDO to three counters (of which I have no way of knowing if any are accurate), I found that the GPSDO now shows 5 bars (it was 3) and Lady Heather has now rendered the satellite map in the upper right hand corner.
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The BG7TBL is running a-ok with Lady Heather when connected via a RS232 cable to a standard RS232 port on a PC. With a USB to RS232 cable I can get some communications between Lady Heather and the BG7TBL but I can't figure out how to get the basic receiver command going. Might be a problem with the pin mapping on my USB to RS232 cable (I've tried two), or maybe I just need to figure out the command. The auto /rx command doesn't work. Is there a way when I'm connected via the RS232 cable to interrogate something to figure out what the preferred command is so that when I reconnect with the USB cable that I can tell Lady Heather what it needs? Or maybe there is something amiss with the USB cable in case anyone has a link to a USB cable known to work (on Amazon, etc.)? Thx
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In case this helps anyone understand what is coming and going on what pins at the BG7TBL RS232 port in your own projects, or in case anyone has any suggestions on how to make this work with a USB cable, that would be cool. Thx
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You need to tell Heather what serial port number that the OS is mapping the USB converter to (use the Windoze device manager). To set the com port number use the /# command line option where # is the com port number... also note that Linux,etc is a bit different). If you don't specify a port number Heather will use COM1.
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That was the first thing I did with the USB/RS232 cable - I set the port to Com1. I verified that the command was working by changing it to Com2, and then back again to Com1. Lady Heather displays the Com port very prominently. I also set the speed, etc. Those steps gave me some confidence that the BG7TBL and the PC were at least communicating at some minimal level with the USB/RS232 cable.
In the eBay ad it says:
4.3 Connect PC
GPSDO-DB9 PC-DB9
PIN2--------------------PIN2
PIN3--------------------PIN3
PIN5--------------------PIN5
PIN8--------------------PIN8
GPSDO-DB9 PIN2,PIN5,PIN8 is connect to PC-DB9 PIN2,PIN5,PIN8,
Baud rate is 9600BPS,Baud rate is fixed.
Normally, I would expect Pin 2 (RX) to talk to Pin 3 (TX) but I confirmed with the seller that the pins assignments are as specified in the eBay ad. The seller refers to his pin assignments (above) as "direct connect". In fact I confirmed that the cable I am using is "direct connect" by checking continuity from one connector end of the cable to the other connector.
(And I'm certain that with the PC's RS232 port the BG7TBL is working fine with Lady Heather - so I'm very confident that the software and the GPSDO play well together).
In case it helps, in the photos I posted above there is green activity on the 2 RX, 3 TX, and 8 CTS pins - as the eBay seller specified in the ad. 4 DTR and 7 RTS are permanently red. That leaves 5 GND (which the seller acknowledges is in use) plus no activity on 1 DCD, 6 DSR, and 9 RI - none of which we would expect would be used.
So I'm guessing that the USB to RS232 cable that I'm using is wired differently than as per the "direct connect." I don't quite get the USB architecture and how it maps to some or all of the pins on a DB9 - but with the USB to RS232 cable some commands (such as port, speed, etc.) are getting through - but the /rx auto receiver command isn't working and none of the other commands to set the receiver type are working (I tried them all I think).
Either I need to figure out the command to set the receiver using the USB/RS232 cable (similar to how I set the Com port and speed), or I need to get a better/different USB/RS232 cable. (The RS232 to RS232 connection is fine on the current PC but most other computers are not going to have a DB9 RS232 port and will need a USB port).
You need to tell Heather what serial port number that the OS is mapping the USB converter to (use the Windoze device manager). To set the com port number use the /# command line option where # is the com port number... also note that Linux,etc is a bit different). If you don't specify a port number Heather will use COM1.
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Ok, problem solved.
Sometimes you have to learn older technology before you can deploy newer technology.
It turns out there were two problems.
As mentioned above some of the data was being conveyed between the PC's USB port and the BG7TBL's DB9 port - such as the Com port command. For example I could change between Com1 and Com2, but other commands such as the /rx auto receiver command did not communicate from Lady Heather to the BG7TBL.
The first issue is that Windows mapped the USB port I was using to Com8. I should have found this earlier/quicker. Lady Heather was showing me that I could change to Com1 or Com2 - so it was displaying the port commands but obviously that wasn't fixing the problem because the PC had assigned Com8 to the USB port I was using. However, this still didn't fully fix the problem as Lady Heather still couldn't find a specific receiver even when I set Lady Heather to Com8.
So, second/next I found a null modem adapter. With some continuity testing I had found that various (standard?) RS232 cables do in fact map pin 2 (TX) on one end to Pin 3 (RX) on the other end. And as I mentioned earlier, the cable that I initially used to go from the DB9/RS232 port on the PC to the DB9 port on the BG7TBL had a different straight through wiring such that Pin 2 talked to Pin 2 and Pin 3 talked to Pin 3 (and I think 8 talks to 8, etc.). So, on this cable I tested the null modem adapter (see photo) below and found that it preserved the straight through continuity of my working (but maybe non-standard?) RS232 cable. So then I put the null modem adapter (see photo) on the USB to RS232 cable (at the DB9 end of course), and voila, all is good.
When I open Lady Heather with the USB to RS232 cable with the null modem adapter connected to the BG7TBL I have to first tel Lady Heather that I'm on Com 8 with /8, and then I give it the auto receiver /rx command and everything works.
With the RS232 to RS232 "direct connection" cable Lady Heather starts completely on it's own because Lady Heather starts at Com 1 (where my RS232 cable happens to be plugged in) and then Lady Heather automatically goes into the /rx routine (or some similar default).
So, if you happen to have a RS232 port set to Com1 on your computer and you have a "direct connect' (straight through) cable with a DB9 on each end, this is the easiest way to start up the BG7TBL. If you have standard RS232 cable you will probably need a null modem adapter or redo the pin connectivity to make the wiring"straight through". Likewise, you might also need to do this depending on your USB to RS232 cable is wired (if you are going from USB to DB9).
Long story short, I think that BG7TBL thought that the "direct connect" wiring approach had some advantage over conventional RS232 wiring but when people see a DB9 they assume RS232 and I'm betting this has been the source of some head scratching - both for people who have been using DB9/RS232 to DB9/RS232 cables, and for people using USB to DB9/RS232 cables.
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Another rookie question:
Is the accuracy of the 10 MHz output from the BG7TBL dependent on the quality of the composite satellite signal, or is it binary?
In other words, if the satellite signals are good enough to establish a Lock condition then the internal oscillator is going to be the determining factor? Or does a relatively stronger GPS input signal make a relatively more accurate 10 MHz output signal?
For example, I see the LCD on the BG7TBL move around in the range of 999,999.9997 Hz to 10,000,000.0000 Hz. I could just be imagining things but it seems that when I have the antenna positioned for a relatively better view of the sky which produces higher SNRs the LCD is more likely to stay stable at 10,000,000.0000 Hz, and when I move the antenna to a lesser view and get lower SNRs the LCD is more likely to be at 999,999.9997 Hz or so.
Thx
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More tracked satellites and a high SNR will always give you the best and most accurate lock and lowest jitter. However, the accuracy does not diminish significantly with a mediocre SNR and only a few satellites tracked, there will be more jitter and short term stability will be reduced slightly.
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Cool! Thanks!
More tracked satellites and a high SNR will always give you the best and most accurate lock and lowest jitter. However, the accuracy does not diminish significantly with a mediocre SNR and only a few satellites tracked, there will be more jitter and short term stability will be reduced slightly.
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A little off thread topic, sorry - but this might help others who have been on the fence about adding a GPSDO.
After thinking about GPSDOs for awhile (couple years?) and now finally having one for a weekend, I'd say go for it!
I had a hunch installing a GPSDO would be a learning experience - and it has been on a two levels: 1) learning about GPSDOs and Lady Heather, and 2) seeing what happens when you can see frequency and time with better accuracy.
Having said that, this might be the gateway to TimeNuts land (said affectionately).
I'm now pretty sure that my HP 5315A is good to within 1 Hz at 10 MHz. My 5327B is out about 6 Hz at 10 MHz but that's 1 Hz better than I previously thought - and discounted for the cool factor of Nixie Tubes I'd say it's spot on (just kidding, but it was mostly acquired because I like looking at the Nixie Tubes, go figure.)
Anyway, that's mostly the good news. I'm now pretty sure that my 33522B could be off about 1 Hz on 10 MHz. That's kind of disappointing but the good news on that is that when I drive it with the BG7TBL it snaps into time alignment. So, the BG7TBL has (I think, I'm pretty sure) tuned up my reference generator.
Back to the good news or the bad news depending on how you look at it. The Tek 2247A was not very close on on frequency; I had a hunch but now I'm sure. The good news is that it has an input for 10 MHz and with the BG7TBL it snaps into what looks like an accuracy of ~1 Hz at 10 MHz. The 2467B wasn't out as much as the 2247A but it doesn't seem to have an input for an external 10 MHz clock - if anyone knows different, please say.
So, now the question is can I get by with the BG7TBL or is a distribution amplifier needed? It's a slippery slope. YMMV but I have found the BG7TBL to be a very good investment in $ and (haha) time. EF
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Yes, get the distribution amp, I have found it alone cleans up the output from the GPSDO even more. The 2247a has a standard crystal for the counter, not a TCXO, so only expect a few PPM or 5x10 -6 and its going to be temp sensitive. The good news, its easy to adjust, trim cap next to the crystal, rear of the scope on the top board. But dont expect any long term accuracy out of it.
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Thanks for the tip on the 2247A, I was sure the control was in there somewhere but figured it was buried - sounds pretty accessible. And thanks for the heads-up on what to expect. Knowing the threshold of what is good enough can save a lot of time finding it :)
Do you have a link to the distribution amp you like? Thx again.
Yes, get the distribution amp, I have found it alone cleans up the output from the GPSDO even more. The 2247a has a standard crystal for the counter, not a TCXO, so only expect a few PPM or 5x10 -6 and its going to be temp sensitive. The good news, its easy to adjust, trim cap next to the crystal, rear of the scope on the top board. But dont expect any long term accuracy out of it.
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The BG7TBL distribution amp works very well and if your going to use the GPSDO to feed it there is no need for the OCXO in the distribution amp. I read someone who found the combination of the internal OCXO while being fed an external ref caused increased IMD.
https://www.ebay.com/itm/10MHz-Distribution-amplifier-frequency-standard-8-port-output/121714097936?epid=869843952&hash=item1c56b9bf10:g:fjEAAOSw23NZoQQO (https://www.ebay.com/itm/10MHz-Distribution-amplifier-frequency-standard-8-port-output/121714097936?epid=869843952&hash=item1c56b9bf10:g:fjEAAOSw23NZoQQO)
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Here is a review (and some measurements) of the distribution amplifier:
http://www.reeve.com/Documents/Articles%20Papers/Reeve_10MHzDist.pdf (http://www.reeve.com/Documents/Articles%20Papers/Reeve_10MHzDist.pdf)
It seems to be good but a cheaper option is to use a video distribution amplifier and modify it from 75 ohm to 50 ohm (or not bother modifying it and just use 75 ohm cable):
https://xdevs.com/doc/Extron/Extron_ADA_6_modifications_for_use_as_10MHz_distribution_amp_STEINMETZ.pdf (https://xdevs.com/doc/Extron/Extron_ADA_6_modifications_for_use_as_10MHz_distribution_amp_STEINMETZ.pdf)
https://www.jackenhack.com/reference-10-mhz-distribution-amplifier/ (https://www.jackenhack.com/reference-10-mhz-distribution-amplifier/)
There has been quite a lot of discussion on these forums on the latter approach and there is a lot of material on-line
https://www.eevblog.com/forum/testgear/diy-10-mhz-distribution-amplifier-requirements-gathering/ (https://www.eevblog.com/forum/testgear/diy-10-mhz-distribution-amplifier-requirements-gathering/)
Gerry Sweeney built his reference into the distribution amplifier as there is a lot of spare space:
https://gerrysweeney.com/build-a-10mhz-rubidium-frequency-standard-and-signal-distribution-amp-for-my-lab/ (https://gerrysweeney.com/build-a-10mhz-rubidium-frequency-standard-and-signal-distribution-amp-for-my-lab/)
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Another day, another impression.
There is something soothing about seeing all the 0s on the counters and seeing waveforms on scopes that are just rock solid with no drift.
I'm starting to think that if I were to purchase any more test equipment I'd probably make sure there is a 10 MHz input included with almost anything I'd consider.
Given the overall investment in test equipment the price of a GPSDO as a frequency and clock source seems like a very good investment.
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Another day, another impression.
There is something soothing about seeing all the 0s on the counters and seeing waveforms on scopes that are just rock solid with no drift.
I'm starting to think that if I were to purchase any more test equipment I'd probably make sure there is a 10 MHz input included with almost anything I'd consider.
Given the overall investment in test equipment the price of a GPSDO as a frequency and clock source seems like a very good investment.
It is amazing that for very little money you can acquire a source with an accuracy far higher than most expensively equipped labs a few decades ago. An accuracy of 10^-11 means the error over one second is the time span than light takes to travel just 3 mm!
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Another day, another impression.
There is something soothing about seeing all the 0s on the counters and seeing waveforms on scopes that are just rock solid with no drift.
I'm starting to think that if I were to purchase any more test equipment I'd probably make sure there is a 10 MHz input included with almost anything I'd consider.
Given the overall investment in test equipment the price of a GPSDO as a frequency and clock source seems like a very good investment.
It is amazing that for very little money you can acquire a source with an accuracy far higher than most expensively equipped labs a few decades ago. An accuracy of 10^-11 means the error over one second is the time span than light takes to travel just 3 mm!
Roger that. Taped to one of my pieces of gear is a chart that reminds me that in 1ps light travels .3mm :)
But now that we have a taste it's hard not want some more ......
So, more rookie questions:
I'm thinking about deploying the distribution amp with several identical length and terminated coax cables for the various pieces of test equipment. I have a line on some good coax but each cable might need a specific (SMA to BNC) adapter to keep everything uniform. I'm not too worried about the ~0.1 ? dB loss from the adapters, but I'd like to avoid taking the fairly precise setup that is evolving and introduce unwanted reflections, waveform distortions, and maybe/especially any out of phase conditions. I'll do some experimenting but any advice on how to keep things pristine would be appreciated. For example, there will be a connection from the GPSDO to the distribution amp and then connections from the distribution amp outputs to each piece of TE. The TE interfaces will generally be BNC (but as mentioned my cables will require a SMA to BNC adapter); more to the point, each piece of TE will have a 50 Ohm BNC interface. Am I going to want to come up with ~6-8 50 Ohm through terminators (one for each dist amp output connector), and is it also necessary to then put 50 Ohm through terminators on the GPSDO 10 MHz output and the distribution amp input?
Thanks!
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In Lady Heather is there a way to figure out which of the colorful satellite symbols displayed on the satellite positions map are associated with the specific PRNs in the PRN/AZ/EL/SNR table? (I've read the LH manual but might have missed it.)
(It would be cool if you could click on a PRN and have it highlight the satellite on the map, and/or vice versa.)
Update: problem solved. Just needed to stare at it and think about it longer. The colored numbers in the four corners pretty much spell it out. I was initially trying to see those numbers as the SNRs for the satellites in their respective quadrants but that didn't make sense given the relative sizes of each satellite (which I knew did/does reflect their relative signal strengths); in fact, the colored numbers in the corners are the PRNs, and the arrows (if present) show the direction being taken by each satellite.
And I think if you have a Signal strength vs as/el graphic that shows a wide range of signal strengths that you will find the strongest areas of coverage correlate to where you generally see the "strongest" ("biggest") satellites on the satellite position map.
The math and code (not to mention the understandings of physics and technology) that was required to develop LH must be very very cool.
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The shortest time step is the time that a photon needs to travel the Planck distance.
This timestep is 10^(-44) seconds. We have to wait a while for this barrier to show up.
Or fill the gap with more phyisical knowledge. Wiki:
time unit is the time required for light to travel a distance of 1 Planck length in a vacuum, which is a time interval of approximately 5.39 × 10 −44 s.[1] The unit is named after Max Planck, who was the first to propose it.
The Planck time is defined as:[2]
{\displaystyle t_{\mathrm {P} }\equiv {\sqrt {\frac {\hbar G}{c^{5}}}}} {\displaystyle t_{\mathrm {P} }\equiv {\sqrt {\frac {\hbar G}{c^{5}}}}}
where:
ħ = h⁄2π is the reduced Planck constant (sometimes h is used instead of ħ in the definition[1])
G = gravitational constant
c = speed of light in vacuum
Using the known values of the constants, the approximate equivalent value in terms of the SI unit, the second, is
{\displaystyle 1\ t_{\mathrm {P} }\approx 5.391\,16(13)\times 10^{-44}\ \mathrm {s} ,} {\displaystyle 1\ t_{\mathrm {P} }\approx 5.391\,16(13)\times 10^{-44}\ \mathrm {s} ,}
where the two digits between parentheses denote the standard error of the approximated value.
https://en.wikipedia.org/wiki/Planck_time
Frans
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In Lady Heather is there a way to figure out which of the colorful satellite symbols displayed on the satellite positions map are associated with the specific PRNs in the PRN/AZ/EL/SNR table?
The next version lets you put the mouse cursor in the satellite map and it shows the info for the nearest satellite below the map. Also if you display the satellite map as a full screen zoomed image, the satellite system identifier letter is shown on the satellite.
Also the next version will show the signal level at the mouse cursor below the signal level map (as long as there is enough space on the screen to show it). Also the algorithm for coloring in the signal level map has been improved.
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In Lady Heather is there a way to figure out which of the colorful satellite symbols displayed on the satellite positions map are associated with the specific PRNs in the PRN/AZ/EL/SNR table?
The next version lets you put the mouse cursor in the satellite map and it shows the info for the nearest satellite below the map. Also if you display the satellite map as a full screen zoomed image, the satellite system identifier letter is shown on the satellite.
Also the next version will show the signal level at the mouse cursor below the signal level map (as long as there is enough space on the screen to show it). Also the algorithm for coloring in the signal level map has been improved.
Cool!
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The shortest time step is the time that a photon needs to travel the Planck distance.
This timestep is 10^(-44) seconds. We have to wait a while for this barrier to show up.
Or fill the gap with more phyisical knowledge. Wiki:
time unit is the time required for light to travel a distance of 1 Planck length in a vacuum, which is a time interval of approximately 5.39 × 10 −44 s.[1] The unit is named after Max Planck, who was the first to propose it.
The Planck time is defined as:[2]
{\displaystyle t_{\mathrm {P} }\equiv {\sqrt {\frac {\hbar G}{c^{5}}}}} {\displaystyle t_{\mathrm {P} }\equiv {\sqrt {\frac {\hbar G}{c^{5}}}}}
where:
ħ = h⁄2π is the reduced Planck constant (sometimes h is used instead of ħ in the definition[1])
G = gravitational constant
c = speed of light in vacuum
Using the known values of the constants, the approximate equivalent value in terms of the SI unit, the second, is
{\displaystyle 1\ t_{\mathrm {P} }\approx 5.391\,16(13)\times 10^{-44}\ \mathrm {s} ,} {\displaystyle 1\ t_{\mathrm {P} }\approx 5.391\,16(13)\times 10^{-44}\ \mathrm {s} ,}
where the two digits between parentheses denote the standard error of the approximated value.
https://en.wikipedia.org/wiki/Planck_time
Frans
Future generations of EEVbloggers will need a better "GPSDO", some successor to texaspyro's version of Lady Heather, a better "distribution amp", and cables with a really good Velocity Factor to handle this. :)
And the level of precise machine synchronicity (and possibly human thinkronicity) that might come with this would probably be astonishing. I think we might be in a golden era of "it's inexpensive enough for lots of people to have access to amazing stuff by historical standards and there's room for lots of freedom and creativity to learn, apply, and enjoy it" - without being completely chained to it. Hopefully the golden era will just expand and get better. Knock on wood.
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Near the center top of Lady Heather's main screen are values for PDOP, HDOP, and VDOP. In the pdf manual there is one lonely reference to PDOP and none (that I found) for HDOP and VDOP.
In case anyone wants some info on these, here you go:
https://www.anatumfieldsolutions.com/What-is-PDOP-And-Why-its-Obsolete_b_43.html (https://www.anatumfieldsolutions.com/What-is-PDOP-And-Why-its-Obsolete_b_43.html)
Spoiler alert: according to the article it seems we should be somewhat happy with less than 4 for PDOP. I've been watching to see if there is any correlation between PDOP (and HDOP and VDOP), the DOP line in the graph, and the proximity of the LCD readout to 10 MHz (10,000,000.0000Hz). Only briefly (for a few seconds) have I seen a PDOP slightly over 4, mostly it's in the high 1s to lower 2s, and currently it's 1.97 - and it's 4 zeros to the right of the decimal point in the LCD Hz counter. Oops, PDOP just went to 1.91 (lowest I've seen) but the LCD Hz counter went to .0001 briefly, and then back to .0000.
Lowest HDOP I've seen is 1.04 and lowest VDOP is 1.59 - but I've only been watching for about 30 minutes (an hour ago I didn't know these things even existed.) Just hit 1.90 on PDOP but it's very slowly toggling between .0001 Hz and .9999 Hz. I'm guessing the GPS and the OCXO are chasing each other around. Now it's back to .0000 at a PDOP of 1.99. Guess we have some more #s to watch. :popcorn:
So within the category of Time Nuts might be a category of PDOP Nuts. I'm thinking there is probably a cure for this or it's just temporary. (until something new to measure comes along)
Update: new best #s below but I'm guessing given my limited antenna view that guys with better antennas and much better views of the sky are getting much lower numbers.
Update: My bad, should have done a search around here first. Turns out people have been talking about these #s since Dec 2014. But I'm still feeling sort of like Columbus discovering a new land (when people were already living there).
Speaking of sailing, time, lat, and long if you haven't seen this it's pretty amazing (not the video quality but the content):
https://www.youtube.com/watch?v=LHvt48S9l4w (https://www.youtube.com/watch?v=LHvt48S9l4w)
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Depending upon the device type there can be HDOP, VDOP, PDOP, TDOP, GDOP, EDOP, and NDOP (alas, no BeBopDOP). The DOP plot is the average of all the various DOP values the receiver sends. Probably the most relevent DOP for GPSDOs is TDOP.
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Roger that and Thanks texaspyro.
Now that I know TDOP is a thing, I was able to search on it along with some of it's other relatives :)
https://the5krunner.com/2018/07/18/gps-accuracy-hdop-pdop-gdop-multipath-the-atmosphere/ (https://the5krunner.com/2018/07/18/gps-accuracy-hdop-pdop-gdop-multipath-the-atmosphere/)
https://www.gsat.us/support/glossary/tdop (https://www.gsat.us/support/glossary/tdop)
https://nptel.ac.in/courses/Webcourse-contents/IIT-KANPUR/ModernSurveyingTech/lectureB_11/B_11_3GDOP.htm (https://nptel.ac.in/courses/Webcourse-contents/IIT-KANPUR/ModernSurveyingTech/lectureB_11/B_11_3GDOP.htm)
https://en.wikipedia.org/wiki/Dilution_of_precision_(navigation) (https://en.wikipedia.org/wiki/Dilution_of_precision_(navigation))
http://www2.unb.ca/gge/Resources/gpsworld.may99.pdf (http://www2.unb.ca/gge/Resources/gpsworld.may99.pdf)
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First Question: Is 37 the currently correct value for the UTC leap second offset in a GPSDO?
Does manually changing that field have any impact on any of Lady Heather's calculations, or anything else with respect to GPSDO use?
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https://en.wikipedia.org/wiki/Leap_second (https://en.wikipedia.org/wiki/Leap_second)
A leap second is a one-second adjustment that is occasionally applied to civil time Coordinated Universal Time (UTC) to keep it close to the mean solar time at Greenwich, in spite of the Earth's rotation slowdown and irregularities. UTC was introduced on January 1, 1972, initially with a 10 second lag behind International Atomic Time (TAI). Since that date, 27 leap seconds have been inserted, the most recent on December 31, 2016 at 23:59:60 UTC, so in 2018, UTC lags behind TAI by an offset of 37 seconds.[1]
https://www.timeanddate.com/time/leapseconds.html (https://www.timeanddate.com/time/leapseconds.html)
Last Leap Second in December 2016
The last leap second was added on December 31, 2016, at 23:59:60 UTC. The difference between UTC and International Atomic Time (TAI) increased from the 36 seconds to the current 37 seconds.
Next Leap Second
Based on current predictions, the next leap second should be added on June 30, 2020. However, since the speed of the Earth's rotation is subject to unpredictable short-term variations, the date may still change. Once it is officially announced, we will publish it in our Time Zone News.
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Second question: is the main/big digital clock just a repeat in larger size of the local time in the upper left hand corner of Lady Heather, or is the main/big digital clock intended to display UTC? If so, how do you get the local time in the upper left hand corner and UTC in the main/big digital clock? I have studied the /tz= instructions and I can't figure out how to make both local and UTC time display - I can get one or the other to show in both locations, but I can't figure out how to make LH show both. I know, kind of duh..... |O
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Looks like I found the answer to question 1:
It's 18 seconds vs GPS. The 37 seconds offset is vs atomic clock time.
https://endruntechnologies.com/support/leap-seconds (https://endruntechnologies.com/support/leap-seconds)
http://leapsecond.com/java/gpsclock.htm (http://leapsecond.com/java/gpsclock.htm)
LH does seem to take into account the specified offset for GPS time when T is set for GPS.
It's not so clear what LH is doing to the UTC displayed time when the offset is adjusted. ??
Still curious to know if it's possible for LH to display both local time in the upper left and UTC on the big/main digital clock.
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I compared the antenna that came with the BG7TBL (which in my case was a C & Q GPS DAMA1575AT41 from CAIQIN TECHNOLOGY http://www.cai-qin.com (http://www.cai-qin.com)) with a ANN-MB-00-00 antenna from ublox (https://www.u-blox.com/en/product/ann-mb-series (https://www.u-blox.com/en/product/ann-mb-series)) and it was a little different than what I expected.
Disclaimer - nothing at all about this was scientific, it was just first impressions.
The ublox is larger and heavier and feels very sturdy, but after trying both in the same dozen or so similar locations it seems that they were either tied or the C & Q won each time. In general, in my tree challenged window location, they either both produced one antenna bar next to the antenna symbol on the GPSDO LCD or the ublox produced one bar and the C & Q produced 2 bars.
I tried to take some screen shots of the satellite SNRs in LH each time I changed out the antennas but it's kind of hard to determine much because the satellites are moving of course. However, it did seem from the SNRs and maybe also the number of satellites that had green values vs yellow values that the C & Q was producing either comparable or better results.
They both say RG174 on their attached cables but the ublox cable is a bit thicker (~3.02mm vs ~2.97mm). Maybe there is some attribute that makes the C & Q a better match with the BG7TBL or maybe it's just a better antenna. Or maybe my testing is just a misleading first impression. YMMV
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is the main/big digital clock just a repeat in larger size of the local time in the upper left hand corner of Lady Heather, or is the main/big digital clock intended to display UTC?
The Heather displays whatever time the receiver is sending, possibly adjusted for your specified time zone. If you set Heather to display GPS time (TG command) there will be no leapsecond adjustment. If set to display UTC time (TU command), the time will be UTC. The TZ time zone command lets you set your time zone offset (and time zone name(s)) If a time zone has been set, the UTC time will be adjusted for your time zone. Heather can also automatically adjust for daylight savings time.
The big clock, small clock, and analog watch always show the same time.
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Coax cable attenuation listings (incl RG316):
http://rfelektronik.se/manuals/Datasheets/Coaxial_Cable_Attenuation_Chart.pdf (http://rfelektronik.se/manuals/Datasheets/Coaxial_Cable_Attenuation_Chart.pdf)
Frans
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Photos of BG7TBL 2019-03-25 (1/2)
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Photos of BG7TBL 2019-03-25 (2/2)
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Did you check the "UBlox" modul on version and firmware? And the VFC Voltage at the OCXO?
Because I have changed mine to an UBlox M8T and a brand new UCT 108663-01 double oven.
Works way more stable than the original crap (compared with 3 Rubidium standards).
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Did you check the "UBlox" modul on version and firmware? And the VFC Voltage at the OCXO?
Because I have changed mine to an UBlox M8T and a brand new UCT 108663-01 double oven.
Works way more stable than the original crap (compared with 3 Rubidium standards).
Fennec, just to confirm, you found the M8T to be both a direct replacement and better performance than the M7?
https://www.u-blox.com/sites/default/files/products/documents/NEO-LEA-M8T_ProductSummary_%28UBX-16000801%29.pdf (https://www.u-blox.com/sites/default/files/products/documents/NEO-LEA-M8T_ProductSummary_%28UBX-16000801%29.pdf)
https://www.digikey.com/product-detail/en/NEO-M8T-0/672-1010-1-ND/6150673/?itemSeq=295031672 (https://www.digikey.com/product-detail/en/NEO-M8T-0/672-1010-1-ND/6150673/?itemSeq=295031672)
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Decided to play around a bit, changed out the Ublox NEO-M7 for the NEO-M8T. Took a bit of playing with U-Center to get the MCU to run again and provide data on the LCD display. Had to update the NMEA Protocol Main Talker ID to GPS then everything started working again. Unfortunately, I really have no way to see if this made an improvement or not. Mostly changed out the chip just to play with it.
(https://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/9F9FE137-B3D0-433E-B466-5AD0DF305E59.jpg) (https://s241.photobucket.com/user/wsmc551/media/Elecronics/9F9FE137-B3D0-433E-B466-5AD0DF305E59.jpg.html)
(https://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/86BC8AFF-E099-4C3A-B795-C9993CAEF66D.jpg) (https://s241.photobucket.com/user/wsmc551/media/Elecronics/86BC8AFF-E099-4C3A-B795-C9993CAEF66D.jpg.html)
(https://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/602486D5-8D12-4EC7-A2A9-D449ED534570.jpg) (https://s241.photobucket.com/user/wsmc551/media/Elecronics/602486D5-8D12-4EC7-A2A9-D449ED534570.jpg.html)
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Slightly off topic but after using a BG7TBL I'm trying a Star 4+. Seems like a number of differences (as reflected in the info displayed by LH) but at least one that I can't figure out is the PRNs. On the BG7TBL I don't think I ever saw a number higher than about 51 but in any event I'm almost certain I never saw a three digit PRN. With the Star 4+ I'm getting PRNs in the 130s. The antennas look to be somewhat similar in design and they are sitting about an inch from each other. Any reason/significance the BG7TBL doesn't see higher PRNs (or that the Star 4+ does)?
PS, what's a typical timeframe for the Self Survey to complete upon first startup?
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PRNs around 130 are SBAS/WAAS (augmentation) sats in geosynchronous orbit.
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cool Thx
BG7TBL doesn’t notice them because a different receiver is used?
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PS, what's a typical timeframe for the Self Survey to complete upon first startup?
The site survey should complete in about 24 hours. No provisions to change the interval.
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Fennec, just to confirm, you found the M8T to be both a direct replacement and better performance than the M7?
Yes, simple because my M7N was a fake modul and the M8T can handle rtk raw data to play around with SAPOS.
For a simple upgrade the M8N is good enough. It's way more stable than the M7N.
My next steps are the ublox ZED-F9P and change the cheap internal ublox M8T TCXO to an OCXO.
https://www.u-blox.com/en/product/zed-f9p-module (https://www.u-blox.com/en/product/zed-f9p-module)
Just to play arround with.... I do not really need that accuracy, but's interesting what you can reach with those "cheap" hardware.
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... change the cheap internal ublox M8T TCXO to an OCXO.
Hmm.. been a few weeks since I read about those... Seems those modules have an option for external clock input so one doesn't have to replace that internal clock, just input the OCXO into it (divided down enough). Then again, I'm not sure, the replacement might give better results than just the external clock input.
(See M8T datasheet 1.15.2 "Aiding" with EXTINT.)
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PS, what's a typical timeframe for the Self Survey to complete upon first startup?
The site survey should complete in about 24 hours. No provisions to change the interval.
On my Star 4+ it seems to complete the site survey in less than 24 hours - maybe closer to 6-12 hours? I haven't kept very good track of the time but it's been started and then restarted two more times in the first day and it's completed the survey twice, and is now on it's third startup survey. I realize it could be somewhat warm from prior starts but even the very first survey completed in well less than a day. Not sure why.
Lots of other questions developing.....
(I've read and searched the LH manual but so far haven't found the answers.)
1. Is there a way to display the Star 4+ 10 MHz signal in LH?
2. Doppler looks ver (completely) flat – is this normal? (Kinda expected to see some variation over time.)
3. What does holdover perf POOR mean? (What causes POOR? How can it be improved?)
4. Dly is -77ns, that’s a default set in the unit by the seller for the supplied antenna cable length, or something else?
5. Discipline mode is Normal - is that good or is there something better than Normal?
6. When the survey completes the plots for lat, long, and altitude in the ADEV graph disappear; the values remain displayed above the graph area but the plots disappear; GV toggles the values on and off above the graph area but not the graph plots. Kind of strange.
7. When the survey completes DAMP shows 0.000, GAIN shows -3.500 Hz/V, INIT shows 0.000 V; they are all grayed out.... good/not so good?
8. When the survey completes TC says 200.0 sec - is that good/bad/something that needs adjustment?
Thanks for any info/tips.
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It seems the Timing specific module may perform better for use as a GPSDO rather than precision positioning module. The phase comparison for the Disciplined Oscillator comes from the 1pps timing pulse. From what I have been reading, the Timing specific module employ extra features to minimize time pulse jitter.
I'm still poring over the M8T's datasheet and reference information and noted some settings I want to play with when I get home later.
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3. What does holdover perf POOR mean? (What causes POOR? How can it be improved?)
I think that this is just a reflection of the amount of data it has received. Assuming you have a good signal the holdover performance should move onto being "GOOD" at least that is what mine show.
It is just a measure of how good it thinks its learned (Kalman Filter?) parameters are.
Personally I'm not that worried about holdover performance as I've never known the GPS system stop transmitting and if there were a temporary blip I'd just wait for good signal again.
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4. Dly is -77ns, that’s a default set in the unit by the seller for the supplied antenna cable length, or something else?
For precision timing you would want to compute the antenna cable delay for your particular setup based on the length of coax between your GPS antenna and the receiver.
There are several online calculators available to assist you in doing this for both RF delay and signal loss.
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4. Dly is -77ns, that’s a default set in the unit by the seller for the supplied antenna cable length, or something else?
For precision timing you would want to compute the antenna cable delay for your particular setup based on the length of coax between your GPS antenna and the receiver.
There are several online calculators available to assist you in doing this for both RF delay and signal loss.
Thanks. That's kind of what I was thinking but I was wondering what would have set the current setting to -77 ns. Maybe it is a default that comes up when you set LH for /rx4 (Oscilloquartz Star-4). In any event, I followed your advice and found a Times Microwave calculator and entered RG174, ~5 meters (~16.4'), and I tried both the L1 and L2 frequencies (not sure what was intended there so I tried both as shown in the attachments below). The L1 freq calc gave a warning msg saying the freq exceeds the max tested frequency; both calcs showed the same result: ~25 ns, so I've adjusted that in Lady Heather (using the minus sign as per the LH documentation for Oscilloquartz Star). Of course it's pretty difficult to tell if the new delay value is having any impact on the 10 MHz reference signal, or anything else. But it's fun to try :)
- I guess that makes sense. I think light travels about 30 cm or about 1 foot in a ns, so 25 nanoseconds would be 25' but with a .66 Velocity Factor we'd be back to ~16.4 feet.
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The delay calculations are only needed for absolute phase alignment and will have no bearing on the 10MHz accuracy or stability.
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The warning about the max tested frequency is due to the fact that RG174 coax is rated for frequencies up to 1,000 MHz. Beyond that the signal attenuation is greatly amplified as the frequency increases.
RG174 or equivalent is offered up due to the cheap price per foot. You might would want to consider upgrading your coax as this will greatly benefit SNR an d C/N0 signal levels at the L1 portion of the spectrum for satellite acquisition / tracking.
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The delay calculations are only needed for absolute phase alignment and will have no bearing on the 10MHz accuracy or stability.
Yep, it would seem that phase is the next mountain after frequency. It would be cool to be able to watch the phase shift as the values get entered into LH but I'm guessing there is some system level propagation delay, and I don't know that any of my gear would reflect the phase shift accurately - but it's fun to contemplate.
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The warning about the max tested frequency is due to the fact that RG174 coax is rated for frequencies up to 1,000 MHz. Beyond that the signal attenuation is greatly amplified as the frequency increases.
RG174 or equivalent is offered up due to the cheap price per foot. You might would want to consider upgrading your coax as this will greatly benefit SNR an d C/N0 signal levels at the L1 portion of the spectrum for satellite acquisition / tracking.
Roger that. The next step might be to upgrade the antenna with a better antenna - and an antenna with detachable coax, so the coax could be easily changed out. There's a lot of performance improvement chasing to be done with this amplitude, frequency, and phase nut stuff :)
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My HP 53132A will calculate phase angle to 0.1deg between inputs A and B. But phase alignment is only needed for absolute timing or phase sync of the reference signal. Fun to play with but phase is only important if your have something to compare it against. The 10MHz output will be 10Mhz at all 360deg of phase angle with no loss in accuracy.
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The delay calculations are only needed for absolute phase alignment and will have no bearing on the 10MHz accuracy or stability.
Just to be sure I understand, at some point, if the frequency is very close but the phase is off by more than 360 degrees the frequency would have to be (at least) one unit off, right?
So for example, at 10,000,000.1 Hz if the phase is off 180 degrees, the frequency might be 10,000,000.05 Hz or 10,000,000.15 Hz?
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No, at 360 or 180 deg of phase shift, between lets say a frequency counters reference input and the measured signal, the count will still be perfect as the number of waves are still the same. With older counters that count the waves and use the ref as the gate, phase shifts other than 360 or 180deg could cause an error of one count. Modern reciprocal counters like the 53132a, the phase of the test signal has no bearing on the measurement as they don't count the number of waves, but measures the period then inverts to display the frequency. So phase has no effect of the period of the measured signal compared to the reference.
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No, at 360 or 180 deg of phase shift, between lets say a frequency counters reference input and the measured signal, the count will still be perfect as the number of waves are still the same. With older counters that count the waves and use the ref as the gate, phase shifts other than 360 or 180deg could cause an error of one count. Modern counters like the 53132a, the phase of the test signal has no bearing on the measurement as they don't count the number of waves, but measures the period then inverts to display the frequency. So phase has no effect of the period of the measured signal compared to the reference.
Roger
How about 361 degrees off? Will that cause a modern counter to miss by 1 count (wave)?
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361 deg = +1 deg, only 360 deg in a circle. It could, but + or - 1 count is always a given with any counter.
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Just seems like basically the counter is counting waves and then rounding to the nearest wave (not sure yet how it rounds up or down but I'll let that go). But at some point an extra wave (more than 360 degrees past the previous wave) is going to have to be considered an extra count. This might need a glass of wine or a beer.
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The purpose of the cable delay parameter is to align the PPS output to UTC by compensating for the signal delay in the antenna cable between the antenna and the receiver input.
Some receivers also have a way of compensating for the delay in the PPS output cable (usually the PO command in Heather). Some even have ways of compensating for the delay in the receiver RF circuitry.
Heather's cable delay command lets you specify the delay in nanoseconds (like -77) or feet (-50f) or meters (-15m). You can also specify the velocity factor (like -50f 0.66v).
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Just bumping this back into the thread in case anyone has some of the answers - Thx
Lots of other questions developing.....
(I've read and searched the LH manual but so far haven't found the answers.)
1. Is there a way to display the Star 4+ 10 MHz signal in LH?
2. Doppler looks ver (completely) flat – is this normal? (Kinda expected to see some variation over time.)
3. What does holdover perf POOR mean? (What causes POOR? How can it be improved?)
4. Dly is -77ns, that’s a default set in the unit by the seller for the supplied antenna cable length, or something else?
5. Discipline mode is Normal - is that good or is there something better than Normal?
6. When the survey completes the plots for lat, long, and altitude in the ADEV graph disappear; the values remain displayed above the graph area but the plots disappear; GV toggles the values on and off above the graph area but not the graph plots. Kind of strange.
7. When the survey completes DAMP shows 0.000, GAIN shows -3.500 Hz/V, INIT shows 0.000 V; they are all grayed out.... good/not so good?
8. When the survey completes TC says 200.0 sec - is that good/bad/something that needs adjustment?
9. FW says 0149... any chance that's firmware? If so, is that current? What are the chances it can be updated from somewhere?
Thanks for any info/tips.
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Got a beginner question. I want to get one of these and looking on EBay most of them show the 10 MHz output as for example “10M OUTPUT :SINE WAVE,1Vrms (10-15dBm),square wave,3.3/4.7Vpp”. This suggests it is selectable. Is that true and how do you set it, or is it a hardware option?
What model (date I guess) is best?
Thanks all
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It's not settable. You have to buy the model with the fixed output you want.
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It's not settable. You have to buy the model with the fixed output you want.
The output of the CPLD is a square wave, the sine wave is via a low pass filter. You could just jumper the filter for a square wave if you wanted.
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Just wanted to add, finally getting the ublox NEO-M8T configured, enabled Galileo and tracking 20+ sats now. After a few other configuration changes I can say it seems to lock down to 0.00ppb very quickly and is rock solid. Still sorting through the 400 page book on this chip.
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Still sorting through the 400 page book on this chip.
lol, ya, me too :o)
....finally getting the ublox NEO-M8T configured, enabled Galileo and tracking 20+ sats now.
You just need to set the NMEA Protocoll / Version to 4.1, than you can use all 72 SATs and GPS, Gallileo and GLONASS together.
and check out this suite:
http://www.simonsdialogs.com/category/electronics/gpsdo-10-mhz/ (http://www.simonsdialogs.com/category/electronics/gpsdo-10-mhz/)
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You just need to set the NMEA Protocoll / Version to 4.1, than you can use all 72 SATs and GPS, Gallileo and GLONASS together.
I could be wrong, but I think the setting NMEA protocol to v4.1 enables the position fix flags for Galileo and BeiDou to be sent out of the receiver, but does not affect the Navigation input to the receiver. Regardless, I found that little tidbit of info in Sec 31.1.3 of the Protocol manual, now u-center shows me all the tracked SV's. In order for the BG7TBL MCU to run and update the LCD, I had to set the Main Talker ID to GPS, the MCU does not like the extra flags.
Edit: I had to set the main talker ID to GPS for my older 2017-12 version, the newer 2018-06 does not care and can be left to automatic, this is nice as u-center and LH will properly show the Galileo and BeiDou.
I am using a narrow band L1 Timing antenna now. Going to swap it out for a multiband GNSS antenna, although the L1 narrow band antenna does seem to be receiving Galileo well. Right now I have the GNSS types set for GPS, SBAS, and Galileo.
Edit: Now using a PCTEL GNSS multi band antenna and see BeiDou, GLONAS and Galileo;
https://www.pctel.com/antenna-product/global-gnss-timing-reference-antenna-gnss1-tmg-26n/ (https://www.pctel.com/antenna-product/global-gnss-timing-reference-antenna-gnss1-tmg-26n/)
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I am using a narrow band L1 Timing antenna now. Going to swap it out for a multiband GNSS antenna, although the L1 narrow band antenna does seem to be receiving Galileo well. Right now I have the GNSS types set for GPS, SBAS, and Galileo.
If you want to perform precision timing be sure and disable the SBAS subsystem as per page 66 (19.2 Recommendations - "u-blox M8 Receiver Description Including Protocol Specification R16.")
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If you want to perform precision timing be sure and disable the SBAS subsystem as per page 66 (19.2 Recommendations - "u-blox M8 Receiver Description Including Protocol Specification R16.")
Yeah, I just read over that section again, I thought I saw that once before. I'm not sure if the SBAS subsystem introduces jitter or just delay.
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Now I have two BG7TBL LCD GPSDO's. One with a blue background LCD model 2017-12-16 and a new one with a green lcd background model 2018-06-05. I wanted to update the display on both to show ppb, found a few differences in the display programing command between them, also some information that's not in the very nicely but rouge translated v1.1 manual found here;
https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg1912184/#msg1912184 (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg1912184/#msg1912184)
This is whats in the book;
2. Display UTC Time, with Frequency Error in PPB (recommended)
$GPGTC,2 UTC +0000T*$GPGTC,2 GMT +0000T*
However, I found the 2017 unit accepted the code but gave the time an offset of tens of minutes, this was due to a missing 0 in the time parameter. The correct code was;
$GPGTC,2 UTC +00000T*$GPGTC,2 UTC +00000T*
Also corrected the repeated "UTC".
The 2018 unit also would now say ERROR if the format was not perfect and needed the additional 0 in the string, the 2017 would accept the string but would not display the correct time. Last, the code above with the proceeding + in the time parameter would cause the LCD display to literally display a "+" before the time. To correct this, I replaced the + with an additional leading white-space as such;
$GPGTC,2 UTC 00000T*$GPGTC,2 UTC 00000T*
(https://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/D6A13D6C-051D-49BC-A8EC-17411884C778.jpg) (https://s241.photobucket.com/user/wsmc551/media/Elecronics/D6A13D6C-051D-49BC-A8EC-17411884C778.jpg.html)
(https://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/566F8EFD-5FD7-4255-B181-FB9F42C570CD.jpg) (https://s241.photobucket.com/user/wsmc551/media/Elecronics/566F8EFD-5FD7-4255-B181-FB9F42C570CD.jpg.html)
Since I had a few extra NOS UCT 108663 ovens laying around, I pulled the as shipped Trimble 63090 and replaced it, had to move a dc block cap C34 to position C44 which was unpopulated to route the 10MHz sine wave correctly. Also adjusted the EFC gain to 2x as the 108663 needed 5.6v, by default the EFC gain is 3.3v x 1.5 for a max of 5v. Not sure yet if I will update the u-blox M7 for the M8T on this one. Going to do some comparison between the two.
(https://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/BBEF69AA-81A8-4D8B-9724-6173E58D7AA3.jpg) (https://s241.photobucket.com/user/wsmc551/media/Elecronics/BBEF69AA-81A8-4D8B-9724-6173E58D7AA3.jpg.html)
Also made a closed cell foam insulation hat for the OCXO, I believe the a bit of insulation to reduce external thermal influences is a good thing here.
(https://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/D53EF0F2-E827-4720-8E67-BDF4B97D9CBA.jpg) (https://s241.photobucket.com/user/wsmc551/media/Elecronics/D53EF0F2-E827-4720-8E67-BDF4B97D9CBA.jpg.html)
Last note, while working on the new 2018 unit, I found one row of pins on the LCD connector header on the main board were not soldered, easy fix but this caused the display to blank if you moved the cable at all.
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Also made a closed cell foam insulation hat for the OCXO, I believe the a bit of insulation to reduce external thermal influences is a good thing here.
I'm curious to hear the temps that Lady Heather is reporting with your foam hat. I have a similar oscillator (Oscilloquartz 8663-XS DOCXO) in my unit that runs at about 49.1 - 50.3 while the unit is in it's aluminum enclosure.
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Also made a closed cell foam insulation hat for the OCXO, I believe the a bit of insulation to reduce external thermal influences is a good thing here.
No, it's probably a bad idea. The oscillator ovens were designed to run without any external insulation (and work quite well as is). Adding insulation can upset the balance of the thermal gains of the ovens and interfere with the operation of the internal oven controllers.
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I'm curious to hear the temps that Lady Heather is reporting with your foam hat. I have a similar oscillator (Oscilloquartz 8663-XS DOCXO) in my unit that runs at about 49.1 - 50.3 while the unit is in it's aluminum enclosure.
You must have a OSA Star 4 board, there is no way to pull OCXO temp from the BG7TBL units.
No, it's probably a bad idea. The oscillator ovens were designed to run without any external insulation (and work quite well as is). Adding insulation can upset the balance of the thermal gains of the ovens and interfere with the operation of the internal oven controllers.
Those are some good points, wish I had some way to verify or measure the effects. The same argument has been made with the LTZ1000, the chip works best when it can dissipate some heat and be allowed to regulate itself. My thought was to keep the environment around the OXCO steady, but perhaps this will do more harm than good, simple enough to remove.
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I have one of the original BG7TBL units without a display and this afternoon it failed on me. The red ALM light stays on and the GPS Lock light is off. The Status LED is however flashing and the OCXO is warming up. I see 3.29V at the antenna socket.
Does anyone have some fault finding information?
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I have one of the original BG7TBL units without a display and this afternoon it failed on me. The red ALM light stays on and the GPS Lock light is off. The Status LED is however flashing and the OCXO is warming up. I see 3.29V at the antenna socket.
Does anyone have some fault finding information?
The first thing I would check is if your OCXO has aged out and can no longer be netted back to 10.000MHz. Check the EFC voltage, be default, the EFC voltage range is 0-4.9v. Happened to me not long ago.
This video may help you;
https://www.youtube.com/watch?v=gBkRFT9TgQI (https://www.youtube.com/watch?v=gBkRFT9TgQI)
I made a post on this here;
https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg2255781/#msg2255781 (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg2255781/#msg2255781)
Post a photo of which OCXO you have.
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I have one of the CTS OCXO devices fitted but the problem has been located, my antenna has died after being knocked from the window frame one too many times by the cats. At least, I think it's the antenna as they are not supposed to rattle.
Off to EBay for a replacement, I may get one of the marine units and mount it outside.
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my antenna has died after being knocked from the window frame one too many times by the cats.
double sticky tape.
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my antenna has died after being knocked from the window frame one too many times by the cats.
double sticky tape.
For the antenna or the cats? >:D
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I received my 2019 model blue LCD a day ago (PCB says 2019, but the case back says 2018). The 10 MHz functions and the LCD works, but it's very easy to scramble or blank the LCD. All I have to do is touch the top of the unit. I believe it's a ESD issue. If I leave the unit untouched, it's fine. 10 MHz output works fine during the LCD issue however.
I emailed the seller and they mentioned unplugging the antenna and back in again. And, yes, after 5 seconds or so the display sorts it self out. Not sure I'm finding that as an acceptable situation. The fact the seller came back quickly and with a decisive answer leads me to think this is not the first time they have seen this.
Anyone else?
Update:
Figured out a fix. Shielding. The end plates weren't electrically connected reliably. The whole top and front were floating. Once I sanded the ends of the aluminum and put some conductive tape to allow the end plates to make contact with them, the problem went away.
The design could use some improvement in ensuring all the surfaces make contact with each other.
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my antenna has died after being knocked from the window frame one too many times by the cats.
double sticky tape.
For the antenna or the cats? >:D
yes.
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I received my 2019 model blue LCD a day ago (PCB says 2019, but the case back says 2018). The 10 MHz functions and the LCD works, but it's very easy to scramble or blank the LCD. All I have to do is touch the top of the unit. I believe it's a ESD issue. If I leave the unit untouched, it's fine. 10 MHz output works fine during the LCD issue however.
I emailed the seller and they mentioned unplugging the antenna and back in again. And, yes, after 5 seconds or so the display sorts it self out. Not sure I'm finding that as an acceptable situation. The fact the seller came back quickly and with a decisive answer leads me to think this is not the first time they have seen this.
Anyone else?
Update:
Figured out a fix. Shielding. The end plates weren't electrically connected reliably. The whole top and front were floating. Once I sanded the ends of the aluminum and put some conductive tape to allow the end plates to make contact with them, the problem went away.
The design could use some improvement in ensuring all the surfaces make contact with each other.
The ground for the LCD should be through the ribbon cable and not via chassis ground. I would inspect the ribbon cable connectors and insure they are properly soldered to the boards. I had one where an entire row of pins was not soldered. I have run both of mine on the bench completely apart many times and chassis ground between the front and rear covers is not needed for proper LCD operations.
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The ground for the LCD should be through the ribbon cable and not via chassis ground. I would inspect the ribbon cable connectors and insure they are properly soldered to the boards. I had one where an entire row of pins was not soldered. I have run both of mine on the bench completely apart many times and chassis ground between the front and rear covers is not needed for proper LCD operations.
Yes, thank you for comments. There is indeed ground connectivity to the LCD PCB. I had at the time checked both connector solder joints and they were pretty good quality. Mine also works without any casing around the electronics.
Humidity at the time was a bit low (< 40%) so touching most anything in the house would have caused some static discharge while moving around. This is what I'm fairly sure was causing the LCD to scramble (I have a feeling it was the actual the HD44780 module that was having issues). If I grounded the top case and front panels, no more scrambled LCD's with subsequent touching.
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Hi Guys:
I notice from the postings that there is now a 2019 version of the BG7TBL GPSDO.
For those here who have purchased it, do you know if the frequency is accurate, and
if the previous software bug that caused a small offset has been fixed?
What improvements are in the 2019 version?
Are there any specifications or user manual?
All of the current ebay vendors that have "2019 10MHZ OUTPUT SINE WAVE GPS DISCiPLINED CLOCK GPSDO"
in their product listing, are actually showing a photo of the 2017 unit :-) :-)
Thanks for any initial impressions, opinions, etc.
Neal
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Hello!
For anyone who's interested in the EFC behaviour of the (2016-05-31) BG7TBL GPSDO are here some test measurment results:
[attachimg=1]
I replaced the 5 VDC Bliley OCVCXO by a 12 VDC Trimble 34310-T OCVCXO (as shown below) and I wondered what the EFC voltage behaviour was...
[attach=2]
The replacement was quite easy. The EFC amplification isn't changed and only jumper R5 is moved to position R4 to get 12 VDC to the OCVCXO instead of 5 VDC.
[attachimg=3]
I won't bother you with the details here, so if you're interested in all the details it can be found here: http://www.amateurtele.com/index.php?artikel=203&id=#1380 (http://www.amateurtele.com/index.php?artikel=203&id=#1380) (Due to the international group of users, I translated most if it already from Dutch to English, but it's still work in progress.) 8)
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I notice from the postings that there is now a 2019 version of the BG7TBL GPSDO.
All of the current ebay vendors that have "2019 10MHZ OUTPUT SINE WAVE GPS DISCiPLINED CLOCK GPSDO"
in their product listing, are actually showing a photo of the 2017 unit :-) :-)
Thanks for any initial impressions, opinions, etc.
I received my GPSDO within a week from China to Germany. Super fast delivery. On the front the datecode 2019/03/25 is printed.
The parcel included the BG7TBL GPSDO, a DC wall plug and an GPS antenna. I payed $148 on ebay. Link to eBay offer: https://ebay.us/9W2CF7 (https://ebay.us/9W2CF7) Seller: thanksbuyer-hobby
There is no manual in the parcel. I do not have any equipment which is capable of veryfining the 10MHz output. On the back, there is a sticker with a link to a taobao site: https://bg7tbl.taobao.com/ (https://bg7tbl.taobao.com/)
Best regards
Timber
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Sorry in advance for the "ugly" formatting. Not used to posting via this format...
I had a single BG7TBL Symmetricom Inside GPSDO as a instrument time base. I wanted the ability to test it for accuracy and recently purchased a BG7TBL 2019-03-25 GPSDO for comparison. Initial tests showed the 2019-03-25 unit was about 900uHz low. To confirm accuracy (looks like the song “Does Anyone Really Know What Time It Is” is true), I borrowed a Rhode & Schwarz ED170MP GPSDO and a friend’s (Doug) BG7TBL Symmetricom Inside GPSDO. This post summarizes the results and I have come to the conclusion that the 2019-03-25 unit is not as accurate as the Symmetricom Inside units with a difference of 1E-2 to 1E-3. I don’t profess to be an expert in this area so please let me know your thoughts.
Test Setup
All GPSDOs were powered for at least one week before conducting any tests. All tests run between 24 and 48 hours. The Rohde & Schwarz has its own down converting antenna. The three BG7TBL GPSDOs share a common antenna (Symmetricom 58532A) via a 4 port GPS distribution amplifier (Symmetricom 58536A). Since all 3 share the same antenna, the survey data should be extremely close with respect to position.
Fluke PM6690 Setup
- Time base reference: Rohde & Schwarz ED170MP w/20dB attenuator
- Measurement Time: 10 seconds
- Device under test: 1 of 3 BG7TBLs GPSDO
-BG7TBL GPSDO Date code 2019-03-25 (internal board date code of 2019-01-07 just like the pictures Involute posted)
Photos of BG7TBL 2019-03-25 (1/2)
-BG7TBL GPSDO “Symmetricom Inside” with integral display (Ron’s)
-BG7TBL GPSDO “Symmetricom Inside” (Ron’s)
Results Summary:
Before drilling down into the results of the it appears as though the newest BG7TBL GPSDO (2019-03-25) is only good to 1E-11. In contrast, the earlier “Symmetricom Inside” units which are good to 1E-13 to 1E-14. The presumption here is the Rhode & Schwarz is an accurate reference.
- BG7TBL GPSDO Date code 2019-03-25:
10MHz output: Consistently about 900uHz low, 2 samples provided
1PPS output: Terrible short term (1 minute) stability per the attached scope capture (persistence set to infinite). 2.5 divisions at 20ns per division for a 50ns jitter over a 1-minute interval.
Survey data: Since unit outputs NEMA sentences via the DB9 connector, an analysis of the “$GPGGA” records over about 1000 seconds results in a wide range of positions. This summary and all GPGGA records are in the attached spreadsheet.
Latitude Longitude Altitude
Average 4308.83108 7610.25686 125.8
Min 4308.83043 7610.25545 122.6
Max 4308.83189 7610.25804 131.0
StdDev 0.000430624 0.000811474 1.885299917
- BG7TBL GPSDO “Symmetricom Inside” with integral display (Ron’s)
10MHz output: 14uHz high in the sample provided and typical of other tests
1PPS output: Minimal short term (1 minute) stability with about 1/4 division or 5ns jitter over a 1 minute interval.
Survey data: LAT(N 43:08:49.884) LON(W 76:10:15.426) H(124.50 m MSL)
- BG7TBL GPSDO “Symmetricom Inside” (Doug’s’s)
10MHz output: 1uHz high in the sample provided.
1PPS output: Minimal short term (1 minute) stability with about 1/4 division or 5ns jitter over a 1 minute interval.
Survey data: LAT(N 43:08:49.848) LON(W 76:10:15.384) H(126.00 m MSL)
Ron
WB2WGH
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Another BG7TBL, this dated 2019-02-28 on the enclosure, 2019-07-05 on the board. The antenna voltage is 5v not 3.3v as indicated in the sales info.
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I sent BG7TBL an email regarding the accuracy of the 2019-03-25 unit referencing my eevblog post. Here is his response:
"hello this normal.there is deviation with this type gpsdo.you can see other friend test result.this version is peak to peak is small value. lcd-gpsdo not this problem. thanks bg7tbl"
When queried as to which models do not have the problem the response was:
"this version" with the image included below:
[Note image appears not to be posting. The image is of a unit with a 2017-12-16 date code with the one line display on the side opposing the connectors.]
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"should" be posted at https://www.eevblog.com/forum/testgear/new-gpsdo-bg7tbl/ (https://www.eevblog.com/forum/testgear/new-gpsdo-bg7tbl/) ?
Thanks for the post, I am curious for the difference between the old and the new version (technically), although for my purpose (external reference frequency counter) I am very happy wilt the "old" version.
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I sent BG7TBL an email regarding the accuracy of the 2019-03-25 unit referencing my eevblog post. Here is his response:
"hello this normal.there is deviation with this type gpsdo.you can see other friend test result.this version is peak to peak is small value. lcd-gpsdo not this problem. thanks bg7tbl"
When queried as to which models do not have the problem the response was:
"this version" with the image included below:
[Note image appears not to be posting. The image is of a unit with a 2017-12-16 date code with the one line display on the side opposing the connectors.]
I find BG7TBL's reply difficult to understand, me not being a native english speaker and not familiar with chinese either.
Can someone clarify?
Also, a single unit of a specific date code is not statistically significant.
Have you tested any other identical units?
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I sent BG7TBL an email regarding the accuracy of the 2019-03-25 unit referencing my eevblog post. Here is his response:
"hello this normal.there is deviation with this type gpsdo.you can see other friend test result.this version is peak to peak is small value. lcd-gpsdo not this problem. thanks bg7tbl"
When queried as to which models do not have the problem the response was:
"this version" with the image included below:
[Note image appears not to be posting. The image is of a unit with a 2017-12-16 date code with the one line display on the side opposing the connectors.]
I find BG7TBL's reply difficult to understand, me not being a native english speaker and not familiar with chinese either.
Can someone clarify?
Also, a single unit of a specific date code is not statistically significant.
Have you tested any other identical units?
I believe he means the frequency offset is typical on the version in your thread. The 2017-12 LCD versions do not seem to have this offset.
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Comparing the Trimble vs my NEO-M8T modified BG7TBL GPSDO. HP 53132A, 100 sec count, 100 count statistical mean average. They tend to agree quite well, within 5uHz from 10MHz or <5x10^14
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I've had my BG7TBL GPSDO for a while, bought the distribution amp the other day and very happy with it.
Does anyone know if the issue with the frequency not being exactly on 10 MHz has been resolved in the later revisions?
https://www.youtube.com/watch?v=EgF6-JbGUXA (https://www.youtube.com/watch?v=EgF6-JbGUXA)
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Yesterday I've received my BG7TBL GPSDO from China (aliexpress). The date on the case is 2019-08-03. During startup it is described as BG7TBL 20190123.
I did not open it yet.
Several things I've noticed:
* The screen sometimes stops. It happens sometimes during initialization of Lady Heater. The GPSDO works still, but in order to see the time and frequency on the lcd, I have to restart the device. When I touch the screen on the left side I hear some electric clicks.
* The GPSDO works well with u-center and Lady Heather. See attached screenshot of the satellite view Lady Heather (6.14). The GPS is connected via serial to USB converter for now.
* Was somebody able to configure the u-blox unit via u-center? When I try to send commands, it returns to the previous configuration instantly, but I can do hot/warm/cold reset with it (the lcd screen shows GPS NO FIX for a moment after this), so it seems there is a two-way connection. I would like to change the GNSS satellite configuration to see different satellite types (It's currently set to GPS only I guess – see attached settings, I would like to add GLONASS and/or Galileo).
* Is it possible to use PPS on RS232C to directly discipline NTP server? I guess the 1PPS signal is on the wrong pin of the serial port?
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Photos of the inside. Board date is 2019-01-07.
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Last post for now.
1. I was able to set it to my CET time and ppb by the command:
$GPGTC,2 CET +0200T*$GPGTC,2 CET +0200T*
2. I can confirm that whenever I run Lady Heather 6.14 with -rxu option (u-blox mode to see more data) the LCD screen stops, but the whole device continues to work. No such problem with u-center, or Lady Heather with -rx option (but then much less parameters visible).
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-rxu configures the receiver for binary mode messages. -rx uses NMEA (or whatever the receiver is configured for). I suspect that the GPSDO firmware is not aware of binary mode messages.
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-rxu configures the receiver for binary mode messages. -rx uses NMEA (or whatever the receiver is configured for). I suspect that the GPSDO firmware is not aware of binary mode messages.
It seems only the LCD screen is affected. When I run Lady Heather with -rxu, the LCD stops updating, but Lady Heather shows all the info and everything updates continually. Then when I restart Lady Heather with -rxn (-rx in this situation would be the same as -rxu), the LCD starts working again. It's a pity, as u-blox mode gives much more info (Sawt, Accu, Frac, Dly, FW and HW info of the receiver, Antenna info, PPS (USRPPS), TDOP, NDOP, EDOP, EL, dBc, satellite states, leap second info). Two things differ, and I don't know why: "UTC offs" is 19 in u-blox, 18 in nmea and the altitude is about 30 meters higher in u-blox.
Unfortunately, I found out I cannot change satellite types – this GPSDO uses normal u-blox 7 series chip, which can work only with one type of satellites. Changing some other settings work (until reset).
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I had the same issue with the LCD stopping, see my message a few posts back. I found I had to provide additional grounding to the front and back "PCB panels" on the unit. In my case, just touching the front or back portions of the unit could stop the LCD (the remainder of the unit continued to function).
Also, if you want it back without cold restarting it, just unplug the antenna for a few moments, the LCD will reset and come back.
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I had the same issue with the LCD stopping, see my message a few posts back. I found I had to provide additional grounding to the front and back "PCB panels" on the unit. In my case, just touching the front or back portions of the unit could stop the LCD (the remainder of the unit continued to function).
Also, if you want it back without cold restarting it, just unplug the antenna for a few moments, the LCD will reset and come back.
I've read your post before, but I don't think it's the same issue. I can stop and start the time at will by changing the data protocol. heather -rxu stops the screen, heather -rxn starts it again. In u-center I can switch protocols in Configure - Ports (PRT). "Protocol in" defaults to UBX+NMEA, "protocol out" is NMEA. If I change "protocol out" to UBX or even UBX+NMEA, the time on the screen stops. Unplugging the antenna does not change it. As texaspyro wrote, it must be that GPSDO does not understand binary mode internally.
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Good Evening together
I followed this Tread since a few Weeks and because i found the only Manual for the OSA OEM Star 4+ Board in this Thred, i thougt to Post here. (sorry its not BG7TBL, its amoj1010 ::) )
A few Weeks ago i also got my Board from Ebay, and after some Trying i got it working and finally "Hold perf good" lit up on LH screen. :-+
I decited to dive a little deeper and try to understand How LH works with the Board, made some Improovements to the Interface Board an after some unsuccessfull tryings to comunicate whit the Board directly over Putty, i endede up using termite and it worked great. (you have to send ";<cr><lf>" after every command, and with Putty you have to send <cr><lf> in Binary. Termite lets you just choose to do this automaticly :-+ )
But then i dived to deep.... :palm:
There is a little not further documented command "download", so i gave it a try and hit Enter, what could happen?
The Board sput out the following:"OK;..UART Initialization OK...;..CFI Information OK...;.. FLASH Sector Erase OK...;..Please send SREC Image...;.." :-BROKE *gulp*
OK, i had no Image Handy and i thougt it would downloading something, not uploading :wtf:
Because i was'nt into the Matter at this moment i tryed to exit the Update Mode with several Commands, no luck, at last i did a reset by powering the device off and on. I did many Firmwareupdates in my Life and never thougt this could be a Problem.
Normally you upload the Content, then CRC and Version check, and if you abort, back to Standartd settings. I even have a Dipswitch on my Graficcard to choose a secondary Firmware Storage if the first one crashes.
So far so Bad now, what Happen when you Power off a Xilinx Spartan 3A FPGA? He will loose his configuration! |O
and the Cypress static Ram? It is only "static" while powered on! |O
But hey you got the Atmel Flash Memory, it holds Informations without Power! Yes thats true, but that was the one that sayd goodby first, you remember:"FLASH Sector Erase OK" |O
i had a little Hope first, because it says Sector Erase, that the Inventors of the Board made a locked sector from which i could be able to boot again, i was Probing around some Time but no Luck, the Board is (probably) Dead :horse:
So for Guys like me, dont even try to Type "download" and hit Enter
For all the other Pros around the Forum, if you are able to support me whith a Firmware File, or read out the Contents From the Flash, i will be willing to try out to rescue the Board and give you some Updates about the Process.
Anyone want to test something with the Board, or to Know something specific ist welcome, i will give my best, i consider the Board dead anyway... :-//
Thank you!
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What program are you using to send the command to the unit? I tried PuTTY 0.73 but did not work out how to send the command to serial port.
Now I have two BG7TBL LCD GPSDO's. One with a blue background LCD model 2017-12-16 and a new one with a green lcd background model 2018-06-05. I wanted to update the display on both to show ppb, found a few differences in the display programing command between them, also some information that's not in the very nicely but rouge translated v1.1 manual found here;
https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg1912184/#msg1912184 (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg1912184/#msg1912184)
This is whats in the book;
2. Display UTC Time, with Frequency Error in PPB (recommended)
$GPGTC,2 UTC +0000T*$GPGTC,2 GMT +0000T*
However, I found the 2017 unit accepted the code but gave the time an offset of tens of minutes, this was due to a missing 0 in the time parameter. The correct code was;
$GPGTC,2 UTC +00000T*$GPGTC,2 UTC +00000T*
Also corrected the repeated "UTC".
The 2018 unit also would now say ERROR if the format was not perfect and needed the additional 0 in the string, the 2017 would accept the string but would not display the correct time. Last, the code above with the proceeding + in the time parameter would cause the LCD display to literally display a "+" before the time. To correct this, I replaced the + with an additional leading white-space as such;
$GPGTC,2 UTC 00000T*$GPGTC,2 UTC 00000T*
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I used Realterm program and it worked ok!
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I just received a BG7TBL GPSDO from eBay, "US seller". faceplate date is 2019-08-03, but the back side of the faceplate says 2018-06-05,
and the main board has a date 2019-01-07. this is not a LCD version
OCXO is CTS 196-0017 with a mfg date or 2008 week 8. no info on GPS chip,
but on startup is spits out this, so it seems to be a ublox UBX-M8030 fw 3.01
$GPTXT,01,01,02,u-blox AG - www.u-blox.com (http://www.u-blox.com)*50
$GPTXT,01,01,02,HW UBX-M8030 00080000*7E
$GPTXT,01,01,02,ROM CORE 3.01 (107888)*35
$GPTXT,01,01,02,FWVER=SPG 3.01*58
$GPTXT,01,01,02,PROTVER=18.00*0F
$GPTXT,01,01,02,GPS;GLO;GAL;BDS*69
$GPTXT,01,01,02,SBAS;IMES;QZSS*57
$GPTXT,01,01,02,GNSS OTP=GPS;GLO*29
$GPTXT,01,01,02,LLC=FFFFFFFF-FFFFFFFF-FFFFFFFF-FFFFFFFF-FFFFFFFD*31
$GPTXT,01,01,02,ANTSUPERV=AC SD PDoS SR*20
$GPTXT,01,01,02,ANTSTATUS=DONTKNOW*33
$GPTXT,01,01,02,PF=3FF*55
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I also got a BG7TBL PLL_GPSDO, 2019-02-28 version. This model appears to have an OCXO, isotemp model 131-261B with a data of 2012 week 12
no marking on GPS, but startup spits out Ublox UBX-G70XX rom 1.00
$GPTXT,01,01,02,u-blox ag - www.u-blox.com (http://www.u-blox.com)*50
$GPTXT,01,01,02,HW UBX-G70xx 00070000 FF7FFFFFo*69
$GPTXT,01,01,02,ROM CORE 1.00 (59842) Jun 27 2012 17:43:52*59
$GPTXT,01,01,02,PROTVER 14.00*1E
$GPTXT,01,01,02,ANTSUPERV=AC SD PDoS SR*20
$GPTXT,01,01,02,ANTSTATUS=DONTKNOW*33
$GPTXT,01,01,02,LLC FFFFFFFF-FFFFFFFF-FFFFFFFF-FFFFFFFF-FFFFFFFD*2C
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I ordered one of the BG7TBL "Upgraded GPSDO GNSS Disciplined Oscillator Clock 10MHz +Antenna For GPS+GALILEO" from the original seller on ebay. None of the sellers of this unit are in USA yet so I ordered from the first seller on ebay listing it in HK, China. It says BG7TBL 2019-10-20 on the front. Hopefully it won't take too many weeks to get here to the Arizona desert. The new upgraded units can be ordered with two different SAT constellations configured. GPS+GLAILEO just seemed like a combo I wanted to try. I'm pretty sure you can change this. I don't know anything about an upgraded manual or new commands.
Bill
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Finally just got the shipping notice from China... they've been on holiday break and the Corona virus hasn't helped either. I got the seller to add DHL shipping so it comes by air instead of slow boat from... you know the rest! :-+
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Ok the GNSSDO arrived. I plugged it in with it's cheap little antenna and before I could get the USB-serial cable hooked up it was locked and already on 12 SATS. It literally locked in a few hundred seconds... I'll have to time it because it's the fastest locking GPS I've ever had or seen. Also I hooked the 10MHz output to my 53131 port 1 and one of my Rb standards to port 2 and sampled Ratio port 1 -> port 2.
Bill
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Here it is from the front...
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Ok the GNSSDO arrived. I plugged it in with it's cheap little antenna and before I could get the USB-serial cable hooked up it was locked and already on 12 SATS. It literally locked in a few hundred seconds... I'll have to time it because it's the fastest locking GPS I've ever had or seen. Also I hooked the 10MHz output to my 53131 port 1 and one of my Rb standards to port 2 and sampled Ratio port 1 -> port 2.
Bill
Do you select whether it reports from GPS or Galileo or both? Via the computer/what software?
Beyond the fast lock, how does the 10 MHz signal compare to your other GPSs?
Thx
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Do you select whether it reports from GPS or Galileo or both? Via the computer/what software?
Beyond the fast lock, how does the 10 MHz signal compare to your other GPSs?
Thx
I ordered it this way from HK. It was the first listed "enhanced" GNSSDO from BG7TBL I could find with the later date on the front. You can order it with different constellations set. I chose US GPS and Galileo. I'm guessing you can change the setting but it's not a switch or anything on the device and I'm sure probably not supported by them. When I hook it to my 53131 as an external reference and check it against my two Rubidium standards it's 10MHz right on all the digits my 53131 can display. I think maybe tomorrow I'm going to open it up and look what it's made of. It would be neat if I can get more from lady heather than the default NMEA information but that's dependent on what inside right? Here's what LH looks like after running a little while using the little cheap antenna it came with.
Bill
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The next step is to hook it to my better GPS antenna... a plus +43db Symmetricom antenna. I'm hoping with my Symmetricom 58536A I can safely run my symmetricom sync server that's higher voltage on port 1 powering my Symmetricom antenna and run the BG7TBL off port 2. It's supposed to work that way... we'll see. I've never mixed high and lower voltage GPS together on a splitter before. :popcorn:
Bill
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Update... the newer BG7TBL displays all the ublox info if you pass the flag to it.
Bill
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I also bought one of these, which arrived today (nine days from order to delivery). It turned out to be very easy to change the GNSS system(s) it's originally set for - just use the Heather command "SG", or use U-Center to reconfigure it. GPS + Galileo + Beidou also works well, as shown in the screenshots (all made using just the antenna it came with, indoors).
Regards,
Dave
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Tell the seller these new GPSDO
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Are you guys saying that although the units are advertised as supporting two systems you are actually getting 3 (GPS + Galileo + Beidou)?
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Are you guys saying that although the units are advertised as supporting two systems you are actually getting 3 (GPS + Galileo + Beidou)?
Yes you can enable more than one GNSS constellation but from all I've read if you want accurate timing you should choose one with GPS and not more than one. Mine came with GPS and Galileo and it came with SBAS enabled as well.
Regards,
Bill
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Hello,
@BiggieJohn.
BG7TBL to install a resistance R29, what is its value?
What are the references of U6 and U7?
(https://zupimages.net/up/20/16/n6ve.jpg) (https://zupimages.net/viewer.php?id=20/16/n6ve.jpg)
Thanks.
Regards
Diabolo
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How many Beidou sats are you getting at once? I have skytraq GPS - several years old that supports beidou. Usually I only get one beidou sat at any time but I have not changed the mode and it is available. I find that when it is receiving beidou the position becomes rock solid stable. I am using it with a standard ceramic GPS antenna with no LNA, just a passive Taoglas ceramic patch antenna on a small ground plane (an old DVD) The Beidou does add positional stability, quite a bit. But once its been on for awhile it is stable all the time. Iguess what the beidou sats effect is greatly reducing the time it takes for the 3d fix to calm down in all three directions.
EDIT: BTW I have the GPS1-TMG-26N which looks identical to yours. It will receive GLONASS which is not far from GPS, just a tiny bit higher. I am currently using that with my GPSDO 24/7
I could be wrong, but I think the setting NMEA protocol to v4.1 enables the position fix flags for Galileo and BeiDou to be sent out of the receiver, but does not affect the Navigation input to the receiver. Regardless, I found that little tidbit of info in Sec 31.1.3 of the Protocol manual, now u-center shows me all the tracked SV's. In order for the BG7TBL MCU to run and update the LCD, I had to set the Main Talker ID to GPS, the MCU does not like the extra flags.
Edit: I had to set the main talker ID to GPS for my older 2017-12 version, the newer 2018-06 does not care and can be left to automatic, this is nice as u-center and LH will properly show the Galileo and BeiDou.
I am using a narrow band L1 Timing antenna now. Going to swap it out for a multiband GNSS antenna, although the L1 narrow band antenna does seem to be receiving Galileo well. Right now I have the GNSS types set for GPS, SBAS, and Galileo.
Edit: Now using a PCTEL GNSS multi band antenna and see BeiDou, GLONAS and Galileo;
https://www.pctel.com/antenna-product/global-gnss-timing-reference-antenna-gnss1-tmg-26n/ (https://www.pctel.com/antenna-product/global-gnss-timing-reference-antenna-gnss1-tmg-26n/)
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How many Beidou sats are you getting at once? I have skytraq GPS - several years old that supports beidou. Usually I only get one beidou sat at any time but I have not changed the mode and it is available. I find that when it is receiving beidou the position becomes rock solid stable. I am using it with a standard ceramic GPS antenna with no LNA, just a passive Taoglas ceramic patch antenna on a small ground plane (an old DVD) The Beidou does add positional stability, quite a bit. But once its been on for awhile it is stable all the time. Iguess what the beidou sats effect is greatly reducing the time it takes for the 3d fix to calm down in all three directions.
EDIT: BTW I have the GPS1-TMG-26N which looks identical to yours. It will receive GLONASS which is not far from GPS, just a tiny bit higher. I am currently using that with my GPSDO 24/7
I could be wrong, but I think the setting NMEA protocol to v4.1 enables the position fix flags for Galileo and BeiDou to be sent out of the receiver, but does not affect the Navigation input to the receiver. Regardless, I found that little tidbit of info in Sec 31.1.3 of the Protocol manual, now u-center shows me all the tracked SV's. In order for the BG7TBL MCU to run and update the LCD, I had to set the Main Talker ID to GPS, the MCU does not like the extra flags.
Edit: I had to set the main talker ID to GPS for my older 2017-12 version, the newer 2018-06 does not care and can be left to automatic, this is nice as u-center and LH will properly show the Galileo and BeiDou.
I am using a narrow band L1 Timing antenna now. Going to swap it out for a multiband GNSS antenna, although the L1 narrow band antenna does seem to be receiving Galileo well. Right now I have the GNSS types set for GPS, SBAS, and Galileo.
Edit: Now using a PCTEL GNSS multi band antenna and see BeiDou, GLONAS and Galileo;
https://www.pctel.com/antenna-product/global-gnss-timing-reference-antenna-gnss1-tmg-26n/ (https://www.pctel.com/antenna-product/global-gnss-timing-reference-antenna-gnss1-tmg-26n/)
The GPS-TMG-26N wont see BeiDou, you need the GNSS1-TMG-26N which will. I see 8-12 BeiDou with the GNSS antenna.
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How many Beidou sats are you getting at once? I have skytraq GPS - several years old that supports beidou. Usually I only get one beidou sat at any time but I have not changed the mode and it is available. I find that when it is receiving beidou the position becomes rock solid stable. I am using it with a standard ceramic GPS antenna with no LNA, just a passive Taoglas ceramic patch antenna on a small ground plane (an old DVD) The Beidou does add positional stability, quite a bit. But once its been on for awhile it is stable all the time. I guess what the beidou sats effect is greatly reducing the time it takes for the 3d fix to calm down in all three directions.
EDIT: BTW I have the GPS1-TMG-26N which looks identical to yours. It will receive GLONASS which is not far from GPS, just a tiny bit higher. I am currently using that with my GPSDO 24/7
I could be wrong, but I think the setting NMEA protocol to v4.1 enables the position fix flags for Galileo and BeiDou to be sent out of the receiver, but does not affect the Navigation input to the receiver. Regardless, I found that little tidbit of info in Sec 31.1.3 of the Protocol manual, now u-center shows me all the tracked SV's. In order for the BG7TBL MCU to run and update the LCD, I had to set the Main Talker ID to GPS, the MCU does not like the extra flags.
Edit: I had to set the main talker ID to GPS for my older 2017-12 version, the newer 2018-06 does not care and can be left to automatic, this is nice as u-center and LH will properly show the Galileo and BeiDou.
I am using a narrow band L1 Timing antenna now. Going to swap it out for a multiband GNSS antenna, although the L1 narrow band antenna does seem to be receiving Galileo well. Right now I have the GNSS types set for GPS, SBAS, and Galileo.
Edit: Now using a PCTEL GNSS multi band antenna and see BeiDou, GLONAS and Galileo;
https://www.pctel.com/antenna-product/global-gnss-timing-reference-antenna-gnss1-tmg-26n/ (https://www.pctel.com/antenna-product/global-gnss-timing-reference-antenna-gnss1-tmg-26n/)
The GPS-TMG-26N wont see BeiDou, you need the GNSS1-TMG-26N which will. I see 8-12 BeiDou with the GNSS antenna.
I'm in the Western Hemisphere, at approximately 41 N 74 west Are you in Asia/Australia or Europe? I'd expect you would get more satellites there.
The GNSSRadar web site shows how many sats are visible from a given spot. It's telling me I can only receive one Beidou satellite here. They are geosychronous SVs Also, my receiver was made in 2015. So its not at all new. What kind of ublox chip does the BG7TBL contain under the (tape?) ?
http://www.taroz.net/GNSS-Radar.html (http://www.taroz.net/GNSS-Radar.html)
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How many Beidou sats are you getting at once? I have skytraq GPS - several years old that supports beidou. Usually I only get one beidou sat at any time but I have not changed the mode and it is available. I find that when it is receiving beidou the position becomes rock solid stable. I am using it with a standard ceramic GPS antenna with no LNA, just a passive Taoglas ceramic patch antenna on a small ground plane (an old DVD) The Beidou does add positional stability, quite a bit. But once its been on for awhile it is stable all the time. I guess what the beidou sats effect is greatly reducing the time it takes for the 3d fix to calm down in all three directions.
EDIT: BTW I have the GPS1-TMG-26N which looks identical to yours. It will receive GLONASS which is not far from GPS, just a tiny bit higher. I am currently using that with my GPSDO 24/7
I could be wrong, but I think the setting NMEA protocol to v4.1 enables the position fix flags for Galileo and BeiDou to be sent out of the receiver, but does not affect the Navigation input to the receiver. Regardless, I found that little tidbit of info in Sec 31.1.3 of the Protocol manual, now u-center shows me all the tracked SV's. In order for the BG7TBL MCU to run and update the LCD, I had to set the Main Talker ID to GPS, the MCU does not like the extra flags.
Edit: I had to set the main talker ID to GPS for my older 2017-12 version, the newer 2018-06 does not care and can be left to automatic, this is nice as u-center and LH will properly show the Galileo and BeiDou.
I am using a narrow band L1 Timing antenna now. Going to swap it out for a multiband GNSS antenna, although the L1 narrow band antenna does seem to be receiving Galileo well. Right now I have the GNSS types set for GPS, SBAS, and Galileo.
Edit: Now using a PCTEL GNSS multi band antenna and see BeiDou, GLONAS and Galileo;
https://www.pctel.com/antenna-product/global-gnss-timing-reference-antenna-gnss1-tmg-26n/ (https://www.pctel.com/antenna-product/global-gnss-timing-reference-antenna-gnss1-tmg-26n/)
The GPS-TMG-26N wont see BeiDou, you need the GNSS1-TMG-26N which will. I see 8-12 BeiDou with the GNSS antenna.
I'm in the Western Hemisphere, at approximately 41 N 74 west Are you in Asia/Australia or Europe? I'd expect you would get more satellites there.
The GNSSRadar web site shows how many sats are visible from a given spot. It's telling me I can only receive one Beidou satellite here. They are geosychronous SVs Also, my receiver was made in 2015. So its not at all new. What kind of ublox chip does the BG7TBL contain under the (tape?) ?
http://www.taroz.net/GNSS-Radar.html (http://www.taroz.net/GNSS-Radar.html)
Sorry, I was working off my memory. Looking at U-Center now I see 4 BeiDou and 8 Galileo (this was what I was thinking of).
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How many Beidou sats are you getting at once?
I haven't looked at this forum for a while, but I happened to be looking at Beidou + Galileo last night, and remember counting 9 Beidou and 8 Galileo after the unit had been on for an hour or so, here in Northern England. U-Center was configured to allow 12 max from each system.
Regards,
Dave
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My GPS is either too old or I need to change the Talker ID setting or something like that, will need to check it out using the (skytraq) manufacturers utility. If you see them in northern england then I should be able to see more here in NE US unless my GPS only supports previous generation which is quite possible..
How many Beidou sats are you getting at once?
I haven't looked at this forum for a while, but I happened to be looking at Beidou + Galileo last night, and remember counting 9 Beidou and 8 Galileo after the unit had been on for an hour or so, here in Northern England. U-Center was configured to allow 12 max from each system.
Regards,
Dave
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Wich receiver do you use? Because if you have the simple BG7TBL GPSDO you easely can change the U-Blox module.
https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg2493726/#msg2493726 (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg2493726/#msg2493726)
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This GPS is not used right now in a GPSDO, (although I'd like to try them in one) I have a bunch of very tiny, coin sized navspark (sktraq) minis (cost US $6.75 each) that are quite sensitive GPS/Beidou NAVSPARK GPSs. I use them now in various devices for keeping GPS time, they are very good at acquiring and maintaining a GPS lock. also they can be put into position hold mode.. No TRAIM though. Once stationary, they do settle down into a very small circle, though. The Beidou is kind of old, they are at least 5 yrs old. So its entirely likely that their firmware does not support newer flavor of Beidou, and i can live with that because otherwise they work really well. For a long time I've wanted to build them into a GPSDO, I bet they would make an excellent one. If I do that I will likely use Lars' design.
Wich receiver do you use? Because if you have the simple BG7TBL GPSDO you easely can change the U-Blox module.
https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg2493726/#msg2493726 (https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg2493726/#msg2493726)
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Hmm and what does it has to do with the BG7TBL ?
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With a BG7TBL, which I think has a U-blox 7 receiver, when using u-center, I'm trying to figure out how to use the GNSS config. It lets you select various systems (GPS, Galileo, etc.) and edit min/max, enable, etc. Does it need a send command after doing such edits, or just close the window (and say yes to send), etc. or is there some other way to save the edits? Also, is the software or the receiver smart enough to only allow selection of the satellite system(s) actually being received by the receiver, or will it let you toggle anything to an enabled state?
This is my first experience with u-center - seems filled with possibilities. If anyone has the executive summary on how to quickly get the most of u-center, that would be cool to see/know.
Somewhat off topic, but while we are discussing u-center, I can get the BG7TBL to connect easily to u-center and Lady Heather, but my Star 4+ doesn't seem to want to connect to u-center (it connects nicely to Lady Heather)... maybe there is no u-blox receiver in the Star 4+? Or is there some other reason it doesn't want to communicate with u-center? (kinda stupid question, I know). Thx
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Early versions of the Star-4 based boxes brought out the GPS data (TxD only?) to the RS-232 board. When I figured out the protocol of the Star-4 management port that talks to the GPSDO using TL1 commands, he modified his design to use that port on the RS-232 connector.
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With a BG7TBL, which I think has a U-blox 7 receiver, when using u-center, I'm trying to figure out how to use the GNSS config.
Which BG7TBL model have you got? If U-Center says the receiver is an M7, then it will only only pick up either GPS or Glonass, but not both at the same time. The latest BG7TBL has an M8 chip, which can receive three of the four GNSS systems at once, except for GPS+Glonass+Beidou. If you want all four GNSS you'll need to upgrade to the ublox M9 chip. All is explained in the ublox datasheets for the receiver chips.
After using GNSS Config in U-Center, you need to use the Send button at the bottom of the pane to make the changes active. Note that this only changes the configuration in the volatile memory of the chip, so changes are lost after a reboot. If you want to make them permanent you also need to Save the new configuration (to the non-volatile memory) after the Send command (see the U-Center manual for details). The NAV5 menu allows you to set a minimum elevation mask for all satellites (I use 15 degrees), which produces more accurate results than the default 5 degrees. Most of the other options you can set (lots of them!) are either self-explanatory or not applicable for simple uses. It doesn't really take that long to skim through the manual to find out what else the program can do.
If the U-Center won't connect to the Star 4+ it suggests that it doesn't use a ublox receiver, as the software only works with ublox protocols.
Regards,
Dave
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Note that this only changes the configuration in the volatile memory of the chip, so changes are lost after a reboot.
Yepp, because the Ublox-Modules are Chinese clones and has no flash RAM.
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Hi,
I am trying to get used to my new BG7TBL 2019-10-20 with the u-blox m8/8 (according u-center) and the topic GPS timing is new to me.
It should have GPS and Gallileo enabled.
In the u-center configuration GMMS Config, I can see, that GPS, SBAS, QZSS and GLONASS is configured and enabled.
When I additionally enable Gallileo, the RUN LED stops blinking, but the unit is still running and works also with Lady Heather.
Visual GPS is then not working, although it reports incomming data on the NEMA Monitor.
Any hints for configuring this unit for best timing performance are welcome. Location is Germany.
Thanks
Chris
Edit:
It looks llike whenn Lady Heather is switched from the NMEA mode to the ublox mode, the GPSDO switches also in the ublox mode and the run LED stops blinking.
Switching back to NMEA mode in LH with /rxn will bring the unit back in the "normal" mode and the run LED starts bilking again. Visual GPS also works again then.
This could be the explanation for the unit with integrated display, where the display stops to work as soon as the gps module is switsched to ublos protocol.
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Here the infos from my model:
Front:
GNSS Disciplined Oscillator
BG7TBL 2019-10-20
Bootmessages:
$GNTXT,01,01,02,u-blox AG - www.u-blox.com (http://www.u-blox.com)*4E
$GNTXT,01,01,02,HW UBX-M8030 00080000*60
$GNTXT,01,01,02,ROM CORE 3.01 (107888)*2B
$GNTXT,01,01,02,FWVER=SPG 3.01*46
$GNTXT,01,01,02,PROTVER=18.00*11
$GNTXT,01,01,02,GPS;GLO;GAL;BDS*77
$GNTXT,01,01,02,SBAS;IMES;QZSS*49
$GNTXT,01,01,02,GNSS OTP=GPS;GLO*37
$GNTXT,01,01,02,LLC=FFFFFFFF-FFFFFFFF-FFFFFFFF-FFFFFFFF-FFFFFFFD*2F
$GNTXT,01,01,02,ANTSUPERV=*22
$GNTXT,01,01,02,ANTSTATUS=DONTKNOW*2D
$GNTXT,01,01,02,PF=3FF*4B
$GNRMC,213619.49,V,,,,,,,200620,,,N*66
$GNVTG,,,,,,,,,N*2E
According U-center: u-blox M8/8
Supports GPS, SBAS, Gallileo, BeiDou, IMES, QZSS, GLONASS
PCB date: 2020-04-06
Request for Help:
I accidently set the receiver to the default receiver configuration in u-center.
I suppose, that there have been made custom changes in the configuration for GPSDO use.
I would be thankful, if someone with the same unit, or u-blox module, would send his configuration.
This can simply be done in U-center ->Tools -> Receiver Configuration ->"transfer GNSS ->file"
Chris
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Another set of 2019-10-20 version images.
(https://i.ibb.co/6tv8wrd/IMG-20200625-182753.jpg) (https://ibb.co/6tv8wrd) (https://i.ibb.co/PDZYNMv/IMG-20200625-182811.jpg) (https://ibb.co/PDZYNMv) (https://i.ibb.co/Jcc1szF/IMG-20200625-182740.jpg) (https://ibb.co/Jcc1szF)
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Hello, Hi, I just bought a unit like this and I am having a hard time getting the GPS to sync. Where do you have the antenna placed? It gives me a long time to synchronize and even many days it doesn't. Do you use the included antenna? Thank you very much, regards
Gerardo
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Hi
start a new thread and do not hijack an old one with unrelated posts.
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sorry for the inconvenience, thanks
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Hi Gerado,
my unit (see my post above) locks very fast, within minutes with the supplied antenna inside at the window on the ground floor between rows of 4 store bulidings and only a small segment of free sky. GPS, Glonass and Gallileo activated, locks about 20 sats, of course probably a lot of them via reflections.
Looks like there is an issue with your unit.
You can try with Lady Heather or U-center to connect to the u-blox chip and see whats going on.
Maybe, the antenna is defective?
Chris
Hello, Hi, I just bought a unit like this and I am having a hard time getting the GPS to sync. Where do you have the antenna placed? It gives me a long time to synchronize and even many days it doesn't. Do you use the included antenna? Thank you very much, regards
Gerardo
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Ringmodulator is correct... it should lock onto many SAT's quickly even in a window. It does of course work much better now that I connected mine to the roof antenna through my GPS splitter. If it's a bad antenna (the ones it ships with are cheap) that's an easy fix. I've also heard of some bad solder joints on some units so that might be worth looking at as well.
Bill
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I just spotted this thread - so thought best to post some pictures of my recent arrival.
2020-03-02
Notable observations ...
GPS lock takes about 60 seconds
- I have standard antenna (as shipped) behind glass on window ledge
- must have good 'sky' coverage - location is London.
The OCXO
- ALM led goes off
- temperature stability to be ok
- within 10 minutes
- this sounds 'too good'
- I would have expected more time for the oscillator to be disciplined.
I did however 'run' the device for over 8 hours the day before.
My guess is that the OCXO was already disciplined
- and when 'restarting' the device next day (I'm still testing)
- it takes much less time to get 'disciplined'.
Please feel free to chime-in with your experiences
- and any corrections to my 'noob' observations ;)
So far happy with the performance
- just need to get some 'other' reference to fully test the bg7tbl gpsdo and its OCXO stability :P
See below for some photos - including PCB
-
Give links to buy new GPSDO
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Give links to buy new GPSDO
I bought my unit via amazon.co.uk (have piece of mind - if problem with unit or DOA - can return for full refund - no questions asked)
Just type-in ...
GPS Disciplined Oscillator GPS DISCIPLINED Clock
There may be more than one seller - go for the cheapest - or fastest delivery.
My unit cost GBP120
Good Luck :)
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I just got LH 6.14beta
Trying to run LH with BG7TBL 2020-03-02 GPSDO
LH reports 'no receiver' - after it goes through its default search
I'm using com4 - connection with GPSDO is good - data is flowing.
I think my GPSDO is using Ublox receiver - but not marked
Any suggestions or tests I should do to get LH to recognize the receiver?
Cheers
-
Hi,
use a simple terminalprogramm at 9600 Bd 8N1.
You should see the NMEA data comming in, if everything works OK.
You can use the ublox u-center software to check out the ublox fuctions.
With Lady Heather, specify the comport like starting with heather.exe /4 for com 4.
If it starts, it is in NMEA mode. With /rxu you can switch to the ublox mode.
Switch back with /rxn.
Be sure, to specify the correct comport, check in the system settings.
Regards
Chis
I just got LH 6.14beta
Trying to run LH with BG7TBL 2020-03-02 GPSDO
LH reports 'no receiver' - after it goes through its default search
I'm using com4 - connection with GPSDO is good - data is flowing.
I think my GPSDO is using Ublox receiver - but not marked
Any suggestions or tests I should do to get LH to recognize the receiver?
Cheers
-
Hi,
use a simple terminalprogramm at 9600 Bd 8N1.
You should see the NMEA data comming in, if everything works OK.
You can use the ublox u-center software to check out the ublox fuctions.
With Lady Heather, specify the comport like starting with heather.exe /4 for com 4.
If it starts, it is in NMEA mode. With /rxu you can switch to the ublox mode.
Switch back with /rxn.
Be sure, to specify the correct comport, check in the system settings.
Regards
Chis
Hey Chris - thanks for your help.
At least I was not going crazy.
Yeah - I'm getting data coming into the FT232 'dongle'
I configured my USB driver and set comport to COM1 with appropriate handshake - as you suggested - but the data I am receiving is gibberish - see screen cap picture.
I tried the obvious settings - different baud and handshake - but nothing sensible coming out of the GPSDO and into the computer.
At least I'm not doing the wrong thing - in principle - just need to find what went wrong.
1st stop is to get proper RS-232 cable and try - my parch wires 'work' - but obviously not :palm:
If you can spot something I did wrong from the pics - than that's great - otherwise I will get proper interface.
I guess there is nothing I can set on the GPSDO side - and if it outputs data at the 9600 baud - then I am on the right track.
Thanks
Cheers
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Hi,
you can start LH as heather.exe /1 /rxn
This switches my unit to NMEA mode.
For ublox mode, use heather.exe /1 /rxu
The /1 is for com 1.
In u-blox mode, the run led does not blink, but this is not an issue.
With the command /rxn, this can be restored.
I strongly suggest to try u-center from u-blox. It is on their homepage.
It will autodetect the port speed and mode, you just have to select the correct com port.
https://www.u-blox.com/en/product/u-center (https://www.u-blox.com/en/product/u-center)
Chris
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Hey Chris,
Appreciate your quick response :-+
I did some checking - and put an old HW flow control dongle I had onto the GPSDO RS232 output port - and notices that there are active RTS/CTS line activity.
I will try to wire this into my dongle - which can handle these signals - perhaps this will fix??
I will then certainly try u-blox
BTW - not directly relating to the above - I have purchased another 3 BG7TBL products
The 10MHz Distribution Amplifier,10MHz OCXO Frequency Standard,8 Port Output
The 1Hz-6GHz Frequency Counter.11digit/s@10MHz
and
The WB-SG1 signal generator 1hz-8ghz signal source broad band signal source with band - on - off modulation
Finally - I also got a LCD version of the GPSDO - it was below $100 - so I could not resist the bargain, but not sure if the Chinese supplier will ship when they realize its way less what others charge.
It was through Amazon - so if things go bad - will be able to get full refund.
If you want the links - let me know.
Well all of the above will keep me going for quite some time (pun unintended) whilst I explore this 'time' rabbit hole ;)
Cheers
-
LCD version of the GPSDO - it was below $100
I'm curious. Give a link please. What is its date / version?
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LCD version of the GPSDO - it was below $100
I'm curious. Give a link please. What is its date / version?
Sure, but be careful - the supplier sent me a message - that they wanted me to cancel the order - because the 'unit' was sold.
I did not - and Amazon confirmed it was shipped - so I will need to wait (snail mail) - to see indeed if it was shipped.
Maybe there was genuine misunderstanding - so will give +1 to supplier until otherwise.
I think the 2017-12-16 is the last revision - BG7TBL does not make this unit anymore??
PLEASE correct me if i'm wrong.
I believe there is a post in this thread - that details the programming of the LCD function.
https://www.amazon.co.uk/gp/product/B08D8TR4VW/ (https://www.amazon.co.uk/gp/product/B08D8TR4VW/)
Good luck
Let me know if you manage to purchase and the system / supplier accepts the order ;)
Cheers
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This item cannot be shipped to your selected delivery location. :((((
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This item cannot be shipped to your selected delivery location. :((((
Hmm...
Maybe politics - Amazon has no problem - it must be the supplier - because this item is NOT fulfilled by Amazon directly.
So maybe China Post - has Problem with your location??
If you want check Aliexpress.com - maybe you can find same model for similar price - I just liked the 'safety' of using Amazon when buying from China directly - in case there are shipping problems.
My other order via Amazon - also from China was great service - the Supplier shipped quickly - I received in 9 days
Take Care my Friend :)
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Hi,
you can start LH as heather.exe /1 /rxn
This switches my unit to NMEA mode.
For ublox mode, use heather.exe /1 /rxu
The /1 is for com 1.
You should not have to specify /rxn or /rxu. If the unit is streaming data Heather should be able to auto identify the receiver type.
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My unit BG7TBL 2019-10-20, in the default mode with the Run LED blilnking, LH without /r argument, starts in NMEA mode.
U-blox is is not auto-detected. What works for me is typing /rxu switching LH in ublox mode.
BTW: Is there a possibility in LH to display the estimated accuracy similar to the units with the integrated diplay option?
Hi,
you can start LH as heather.exe /1 /rxn
This switches my unit to NMEA mode.
For ublox mode, use heather.exe /1 /rxu
The /1 is for com 1.
You should not have to specify /rxn or /rxu. If the unit is streaming data Heather should be able to auto identify the receiver type.
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Thanks to everyone who 'chimed-in' to help :-+
I managed to resolve MY problem which was related to my RS232 to USB interface cable
Long story short - it simply was not receiving the data correctly - and as a result - erroneous data prevented LH to identify the GPS receiver in the GPSDO - and subsequently not being able to function.
With a new AND WORKING cable - all is fine - I just had to specify the comport via /4 command (my device was on com4) LH fires up with NEMA receiver detected.
Is there a way to monitor the OCXO frequency drift of the GSPDO with respect to the received GPS reference with LH?
Not sure if this is possible with a NEMA receiver LH configuration.
Any feedback on this once again is most welcome.
Now I have another interesting problem.
I ordered a few more additional BG7TBL devices and received them today.
1. 10MHz OCXO frequency standard distribution amplifier 2019-09-13
2. FA-2 Precision Frequency counter
3. WB-SG1 Wideband Signal Generator (8GHz)
So I am about to enter even a bigger rabbit hole and might need more help from all of you who visit this thread.
First Question
The 10MHz OCXO distribution amplifier
- does anyone have a user manual?
I am puzzled by the RED led on the front which is labeled ALM
I can only assume this is similar to the ALM LED on the GPSDO ??
The operation of this - is to signal when the OCXO has stabilized or been conditioned by the GPS
When you switch-on the GPSDO for first time - the RED LED ALM is 'on' and this stays on for about 10 minutes - then it goes off (as expected)
On the 10MHz OCXO distribution amplifier - when powered-on the ALM LED is 'off' and it stays off no matter what happens.
Is this normal behavior?
Does it only go 'on' when there is some kind of failure ONLY??
Any input on this will be most welcome.
Second Question
The FA-2 Precision Frequency counter is capable of 11 digit resolution.
It has an external 10MHz reference
I presume (have not opened it up as yet) it has its own OCXO inside for the internal clock.
So any Frequency measurements it performs will be in relation to its internal clock
How can we then 'trust' the 11 digit resolution?
Is there some algorithmic technique used to get extra precision and not tied directly to the clock?
My concern is if I connect the GSPDO 10MHz reference to it - it will then report the GPSDO 10MHz frequency as 'perfect' because its using this as a refrence - I guess this is expected behavior.
So as I suspect - I WILL NOT be able to use the FA-2 to measure the GPSDO frequency deviation from true 10MHz
BUT
I will be able to measure ANYTHING else in reference to the assumed perfect 10MHz GPSDO clock.
Which is as expected - you cannot use yourself as a reference to check yourself ... you know what I mean (I hope).
Also, if someone knows of user manual - I am particular interested as to how to 'switch' on or off the LPF (displayed on front LCD display) - it is not responsive to any button sequences I tried. I assume you will be able to 'switch-on' the Low Pass Filter Function - not sure as to how this it to be applied and to what effect - presumably to 'clean-up' the signal where appropriate.
I found an existing thread on this device ...
https://www.eevblog.com/forum/metrology/bg7tbl-fa1-frequency-analyzer/ (https://www.eevblog.com/forum/metrology/bg7tbl-fa1-frequency-analyzer/)
I guess I missed it the first time around |O
Third Question
Has anyone got the WB-SG1 Wideband Signal Generator (8GHz)?
If you do have it - have you got any 'tips' / suggestions / comments??
Thank you everyone - hope you find this post useful - please ask if you want me to do any testing ;)
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@noreply:
To your first question:
It is my understanding, that these 10MHz distibutors come in two versions. One with internal OCXO and the cheaper ones without internal TCXO.
The ALM LED is on, when neither an external 10MHz is detected, nor an internal OCXO is present. I dont own such a unit and this is, what I understood from the ebay descriptions.
To your second question:
You cant pull yourself out of the mud by grabbing your own hair.
If you want to evaluate the GPSDO, you need a better(!) reference to compare it to.
The internal TCXO of the FA-2 is simply not suited for this. The FA-2 can be calibrated against a GPSDO and then be used as a fairly accurate standalone unit.
It has to be recalibrated from time to time to take care of the aging of the internal OCXO.
Chris
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...
The OCXO
- ALM led goes off
- temperature stability to be ok
- within 10 minutes
- this sounds 'too good'
- I would have expected more time for the oscillator to be disciplined.
...
My understanding is, that the ALM LED goes off, as soon as the OCXO has reached its operating temperature.
Chris
Edit:
I did replace the OCXO in my unit with a Morion MV89A. It takes much longer for the ALM LED to go off.
This did make sense as this OCXO with its double oven is quite big and takes much longer to fully heat up.
But to sense this, there should have been a shunt resistor to detect the drop in current for the OCXO and it looks like there is none.
So it looks to be more likely, that the controller looks at the frequency of the OCXO in comparison with the 1pps signal and as soon as the OCXO frequency is below a certain theshold, it switches the ALM LED off.
Just guesswork.
Any better insights on this?
Chris
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Sure, but be careful - the supplier sent me a message - that they wanted me to cancel the order - because the 'unit' was sold.
I did not - and Amazon confirmed it was shipped - so I will need to wait (snail mail) - to see indeed if it was shipped.
Maybe there was genuine misunderstanding - so will give +1 to supplier until otherwise.
I think the 2017-12-16 is the last revision - BG7TBL does not make this unit anymore??
PLEASE correct me if i'm wrong.
I believe there is a post in this thread - that details the programming of the LCD function.
https://www.amazon.co.uk/gp/product/B08D8TR4VW/ (https://www.amazon.co.uk/gp/product/B08D8TR4VW/)
Good luck
Let me know if you manage to purchase and the system / supplier accepts the order ;)
Cheers
OK, I managed to purchase it. It was not barred from delivery in Italy, but let's see... I'll post the results if eventually it does arrive!
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Interesting...
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6603695/ (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6603695/)
A couple excerpts below, more detail in the paper.
“This paper mainly contributes to the assessment of BDS-2, BDS-2/BDS-3, GPS, GLONASS, and Galileo PPP with the observations that were provided by the international Global Navigation Satellite System (GNSS) Monitoring and Assessment System (iGMAS).”
”Galileo has also made good progress in terms of the coverage and precise positioning. BDS and Galileo are basically at the same level as GPS and GLONASS, and they can be well applied to global precise positioning and other application.”
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You can try with Lady Heather or U-center to connect to the u-blox chip and see whats going on
It is NOT an UBlox Device, it is Chineese fake crap.
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UCenter can command the internal GPS!?
What does it enumerate as, what kind of ublox GPS chip is in there?
There is a banner when it first starts up, would you be able to capture it and paste it here?
Still a few views on the last generation of the BG7TBL GPSDO.
Everything is fine also connect to PC with RS 232 cable. U-Center and Lady heaters work easily with this device and the NMEA data is displayed in the software.
best regards
Hello.
No. I wrote U-Center can display the NMEA data. The U-blox neo 7m could not be controlled at the moment.
Another problem I have noticed yet.
On my two notebooks (with docking station) The GPSDO is misinterpreted as any pointing device.
The cursor jumps over the display and menus are activated indiscriminately.
Currently, the set up only works on my old Core2Duo tower.
Jörg
Apologies but I simply couldn't resist - that's an issue best described as the microsoft ball(s up) intelli-mouse driver issue that has persisted ever since win2k through to win10. I did eventually track down a simple to run fix to disable this microsoft nonsense that had afflicted my (and almost everyone elses) usb to serial adapter drivers (FTDI and Prolific types) used to interface to U-blox and other brands of GPS receiver modules relying on a built in serial to usb interface.
Here's a link (probably the one I used - I can't recall for certain now) to an "MS Serial BallPoint Mouse Disabler" <https://qpdownload.com/ms-serial-ballpoint-mouse-disabler/> for anyone else who might be experiencing the same problem or simply just want to guard against being caught out by this "MS mouse driver Balls up" issue in the future.
John
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Does somebody already knows whats behind this "E-GPSDO bg7tbl"?
It looks like its another thing as PLL-GPSDO..
Grr cant copy Ali link here..
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I also can buy it but the reviews / seller classification is realy bad. There are claims for item never arraived. And fake shop because it is too cheap and other things. Cancled my order..
This link was it:
https://www.amazon.co.uk/gp/product/B08D8TR4VW/ (https://www.amazon.co.uk/gp/product/B08D8TR4VW/)
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I also can buy it but the reviews / seller classification is realy bad. There are claims for item never arraived. And fake shop because it is too cheap and other things. Cancled my order..
This link was it:
https://www.amazon.co.uk/gp/product/B08D8TR4VW/ (https://www.amazon.co.uk/gp/product/B08D8TR4VW/)
Interesting - that this is EXACTLY the SAME item and merchant I tried to purchase several months ago via Amazon - yes its a great price.
The Order was accepted and after a few days I got email from supplier telling me that this product is not good and that THEIR Supplier cannot supply - so they cannot ship to me and want to refund IN FULL.
I contacted Amazon - and told them what happened and did NOT want to cancel the order - because they have committed to this sale by virtue of advertising and NOT removing the product - even after they told me they cannot supply it.
Amazon contacted them and asked to TRY to honor the sale - apparently they cannot force the merchant to supply - BUT CAN remove any future listings which are misleading.
In the end I simply gave up - because the merchant - did provide the FULL REFUND and I got another product from another (Also Amazon) supplier.
I suggest you contact Amazon - them them of your experience - and tell them this is NOT just you - the supplier STILL ADVERTISES the SAME product which they clearly cannot supply - Amazon can stop them from doing it further.
Anyway - thought I should share this feedback with you
Take Care
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I also can buy it but the reviews / seller classification is realy bad. There are claims for item never arraived. And fake shop because it is too cheap and other things. Cancled my order..
This link was it:
https://www.amazon.co.uk/gp/product/B08D8TR4VW/ (https://www.amazon.co.uk/gp/product/B08D8TR4VW/)
Interesting - that this is EXACTLY the SAME item and merchant I tried to purchase several months ago via Amazon - yes its a great price.
The Order was accepted and after a few days I got email from supplier telling me that this product is not good and that THEIR Supplier cannot supply - so they cannot ship to me and want to refund IN FULL.
I contacted Amazon - and told them what happened and did NOT want to cancel the order - because they have committed to this sale by virtue of advertising and NOT removing the product - even after they told me they cannot supply it.
Amazon contacted them and asked to TRY to honor the sale - apparently they cannot force the merchant to supply - BUT CAN remove any future listings which are misleading.
In the end I simply gave up - because the merchant - did provide the FULL REFUND and I got another product from another (Also Amazon) supplier.
I suggest you contact Amazon - them them of your experience - and tell them this is NOT just you - the supplier STILL ADVERTISES the SAME product which they clearly cannot supply - Amazon can stop them from doing it further.
Anyway - thought I should share this feedback with you
Take Care
Ok, so I was in this band wagon as well... never received anything, contacted Amazon and worked until i got a higher up supervisor, and it seems, IT SEEMS - mind you - that the reason this and other similar ads for the GPSDO cannot get honored is because the seller has no clue what he is selling, and that he actually thinks the GPSDO is some sort of power inverter for car use - from 12V CC to 240V AC. And then, he cant get it at the price he advertised.
This makes some sort of sense, because if you read carefully the Amazon description, it acutally says:"...Pure Sine Wave Power Inverters Soft-start function AVR - Black".
Plus, I did not notice, but look at the "Customers also viewed these products" bar.
The Supervisor told me that Amazon allows sellers to make "mistakes" and he cannot hold him responsible for the advertisement, since it is correctly listed as a power inverter, as long as the seller refunds in full - which he did to me at least.
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My E-GPSDO arrived today.
It is working but i still have to check how accurate.
I will try to measure it within the next days.
Attached some pictures from inside. PCB is marked with 10.1.2020 BG7TBL
GPS fix is only possible if i put the antenna outside (then within <30s (inside, behind my window there is no fix).
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Hm wonder why the E-GPSDO should be more accurate than the PLL-GPSDO ?
Looks the same (even same PCB marking) except the ocxo number.
But its 7€ more expensive..
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What does the letter "E" stand for?
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I don't know.
Maybe "Expensive" :horse:
Seller has 2 different ones E- GPSDO:
https://a.aliexpress.com/_BU3HTD
PLL-GPSDO:
https://a.aliexpress.com/_BTItxD
With different accuracy. I also asked him what is the difference and he said "accuracy" no further explanations.
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Hm wonder why the E-GPSDO should be more accurate than the PLL-GPSDO ?
Looks the same (even same PCB marking) except the ocxo number.
But its 7€ more expensive..
Isn't it a PLL-gpsdo? I see a 74HC86 xor gate which are used in PPL style gpsdos.
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I asked the seller, he says slightly different hardware and another software. But i don't know where, probably the Atmel.
I will look if i can read out the thing.
Another observation: sometimes it's loosing his fix. I put the antenna outside of my window but even then it's loosing the fix.
Does somebody know if there is something programmed within the flash of the GPS module? I assume it's a NEO-M7N maybe 6M or chinese clone.
Thinking about switching it to a NEO-M9N to get 4 GNSS concurrent. Hope that heps..
I measured it with my DG992 and SVA1032X i got 10.000.012 MHz but it was unlocked....again... grr
Hope this is fixed with a lock..Or my measurement equipment is more off than the GPSDO i don't know doensn't have something better to measure the GPSDO.
I purchased it to get a reference for these 2 devices..so..
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I have a DYI frequency standard with NEO7M and indoor antenna. Typical deviation 10.000.000,001 MHz (<+-1mHz, 1E-10..-11). The accuracy does not necessarily depend on the GPS receiver.
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Ok but whats wrong then?
The Isotemp OCXO looks ok its from 1212 so pretty "young" . But 12Hz off? Or is it my measurment equipment?
I don't know what they have inside but i assume "only" a TCXO.
The Atmel has a "uncommon" crystal frequency (uncommon for my i would expect something like 8MHz or so.) but i don't think this is a problem or?
Indoor antenna? Can you give me a link?
Maybe someone can help. I will also buy another antenna. "Cheap but good" (i would assume) ones are:
https://www.mouser.de/datasheet/2/398/AA.166.301111-1508818.pdf (https://www.mouser.de/datasheet/2/398/AA.166.301111-1508818.pdf)
https://www.mouser.de/datasheet/2/398/AA.162.301111-1508634.pdf (https://www.mouser.de/datasheet/2/398/AA.162.301111-1508634.pdf)
But which one is better? Couldn't find a real difference.
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A $4 antenna from ebay is sufficient. However, I believe that the problem is not the antenna, but the device. It is either defective or the quality is poor. The Chinese very often use very old oscillators.
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So its getting closer... :-D
After several minutes its really close to 10.000.000,xx and somteimes even 9.999.995,2 (statistics on my "counter") but still no fix.
I think if its cold it gets a fix "fast" but its loosing his fix if its getting warm. Antenna is still on the same position but fix is gone.
Or I'm wrong.
Green is constantly blinking, red is permanantly on if its fixed or?
After a few minutes both leds (green and red) are blinking..
Does somebody know if its really rs232 or "only" UART? Will not destory it if i hook it up to my USB-RS232 adaptor?
Hmm don't know whats the issue here.
Now it got a fix even behind my window. Or the GPS Antenna isn't useable below +5°C?
And my Counter now says ist 10.000.000,31 / 9.999.999,23 (mean value).
Maybe the OCXO / GPS Module needed a "burn in"...
But changing the GPS Module / Antenna is maybe still a good idea to get more fix points. Don't know, will take a breath and decide than if i will spent additional 30€...
But my GPSDO was "only" 71€ in sale so still close to 100€ even with part changes...
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Maybe have a look at this thread https://www.eevblog.com/forum/testgear/new-gpsdo-bg7tbl/ (https://www.eevblog.com/forum/testgear/new-gpsdo-bg7tbl/)
There are two versions, lets call them the old and the enhanced version. I have two old versions (one I got by "accident"), comparing the frequency they agree with each other in phase/frequency for at least something like 15 minutes. I have also the the updated (enhanced) version, this one slightly differs with respect to the frequency, not sure how much as I was not able to verify this (yet). In fact I bought the 3rd one, hoping that the known error of the first version had been fixed. Once I will be allowed to go to the office again I can perform further tests.
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I want to drive my 2 devices with a 10MHz reference input from my GPSDO.
1. DG922 Rigol: It says 10MHz ref in 1kOhm AC
2. Siglent SVA1032X: It says 10 MHz ref in 50 Ohm. Probably AC? But not sure..
Can i drive both inputs directly from the GPSDO with 1 BNC T Connector + 2x BNC RG316 1m cables? Or do in need a distribution amplifier board?
1k||50Ohm are ~47 Ohm should be ok?
How should i connect the units? Special chain?:
GPSDO -> DG922 + T Connector -> SVA <-Best one?
GPSDO -> SVA + T Connector -> DG922
SVA<-GPSDO + T Connector -> DG922
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> GPSDO -> DG922 + T Connector -> SVA <-Best one?
I'd do that one.
> Does somebody know if its really rs232 or "only" UART? Will not destory it if i hook it up to my USB-RS232 adaptor?
It's not RS232. It's just UART. I don't have a unit labeled GB7TBL, but one that seems to be a copy. Mine is 0V to 5V output on the "RS232", but it is inverted. They take the UART output of the ublox module, and drive the base of a NPN which inverts the signal. To interface with a UART to USB converter I connected the Tx output to the base of another NPN (through a series 47k) and the collector to my UART input with a 4.7k pullup to the USB 5v. Resistors values not critical, I used ones that were lying on the bench.
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Happy New Year EEVblogers!
1. Just checking to see if a BG7TBL GPSDO should have a PPS pulse that:
a. occurs every second for a duration of 200ms?
b. has an amplitude of 3 volts?
2. (not exactly on topic), same questions for a Star 4+, ie should a Star 4+ have a PPS pulse that:
a. occurs every second for a duration of 50ms?
b. has an amplitude of ~2.5 volts?
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It appears to depend on the model you've got. My LCD display BG7TBL gives a 50mS pulse every second at 3.4v, but the multi-GNSS BG7TBL gives a 100mS pulse at 3.4v. By comparison, my TBolt-E gives a 200mS pulse at 5.2v. No doubt other makes will have different variations on the theme.
I can't say what the Star 4+ outputs, as I haven't got one.
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The pulse with is propably chaneagble.
You have to reconfigure the "fake neo-7" module.
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Correct - I'd forgotten about that. You can change the pulse width using the TP configuration option in U-Center.
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Ok, thanks for the feedback. Looks like the answer is a) it varies by model, and b) it might be / probably is configurable.
When I connect both the BG7TBL and the Star 4+ to a scope and trigger one channel off the other they clearly align the beginning of the pulse. After that of course they are not synchronized due to the differing pulse widths.
fwiw, each GPSDO is attached to it's own patch antenna sitting next to one another with the same view of the sky. The two antennas are similar but not identical.
So on to new questions.
What would you expect would happen when instead of the using the pulse outputs, the two GPSDOs have their 10 MHz ref outputs inputted to the oscilloscope? With one channel triggered off the other, would you expect the beginning of the two sine waves to be synchronized, or not?
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Very unlikely, as different makes / models will probably have different processing circuitry which will introduce slight time differences into the output paths. I have the three different GPSDOs mentioned above connected to a single external antenna via a splitter and identical cables, and they all differ marginally when compared against each other. With different GPSDOs you have to bear in mind that the signal received by any antenna is constantly changing due to atmospheric/tropospheric influences, and the firmware in each unit will have its own way of correcting the errors, so the outputs from each will always be slightly different by default.
Two nominally identical GPSDOs might produce synchronised 10MHz sine waves, but even then I wouldn't count on it - although the difference should be very slight - because of component manufacturing tolerances.
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Very unlikely, as different makes / models will probably have different processing circuitry which will introduce slight time differences into the output paths. I have the three different GPSDOs mentioned above connected to a single external antenna via a splitter and identical cables, and they all differ marginally when compared against each other. With different GPSDOs you have to bear in mind that the signal received by any antenna is constantly changing due to atmospheric/tropospheric influences, and the firmware in each unit will have its own way of correcting the errors, so the outputs from each will always be slightly different by default.
Two nominally identical GPSDOs might produce synchronised 10MHz sine waves, but even then I wouldn't count on it - although the difference should be very slight - because of component manufacturing tolerances.
Thanks. But we should expect that after each GPSDO settles in, while they will not start their 10 MHz sine waves at the same point they should remain consistent in their relative position to one another (minus any small drift, which should be very little)?
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Therein lies the fundamental problem: except for a few random moments, different GPS units will tend to show different positions all the time, as each will apply compensations to the antenna signals in its own way. The differences between them may be only a few cm or mm, but there will always be relative movement between their outputs. Connect them both to an oscilloscope and view the Lissajou figure they create: no matter how long you leave it, the circle or ellipse you see will always be changing over time, sometimes barely perceptibly, other times relatively quickly. There will never be absolute stability from a single GPS unit, let alone two different ones, but the differences (you hope) will be small enough for your required degree of accuracy.
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"2020 Symmetricom LCD GPSDO" has appeared on Ebay. Does anyone have additional information?
https://www.ebay.com/itm/2020-Symmetricom-LCD-GPSDO-10MHz-1PPS-OCXO-GPS-Disciplined-Oscillator/233279321675 (https://www.ebay.com/itm/2020-Symmetricom-LCD-GPSDO-10MHz-1PPS-OCXO-GPS-Disciplined-Oscillator/233279321675)
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Pictures are however from 2019 model!
Maybe "Fixed known errors". The 2019 model restarts when getting wrong data from gps. Don't know if this is fixed. I don't have this new model.
"2020 Symmetricom LCD GPSDO" has appeared on Ebay. Does anyone have additional information?
https://www.ebay.com/itm/2020-Symmetricom-LCD-GPSDO-10MHz-1PPS-OCXO-GPS-Disciplined-Oscillator/233279321675 (https://www.ebay.com/itm/2020-Symmetricom-LCD-GPSDO-10MHz-1PPS-OCXO-GPS-Disciplined-Oscillator/233279321675)
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Therein lies the fundamental problem: except for a few random moments, different GPS units will tend to show different positions all the time, as each will apply compensations to the antenna signals in its own way. The differences between them may be only a few cm or mm, but there will always be relative movement between their outputs. Connect them both to an oscilloscope and view the Lissajou figure they create: no matter how long you leave it, the circle or ellipse you see will always be changing over time, sometimes barely perceptibly, other times relatively quickly. There will never be absolute stability from a single GPS unit, let alone two different ones, but the differences (you hope) will be small enough for your required degree of accuracy.
I replaced a Star 4+ with a second BG7TBL using the same model antennas for both side by side - but I have an antenna cable issue that will take me a few days to iron out before I can make the cables same length.
In the meantime I'm watching the sine waves do their dance relative to one another on an oscilloscope and thinking about what you said.
If two GPSDOs don't stay aligned in phase, but they both keep track of 10 MHz with a fair amount of accuracy, to a pretty small level of resolution, is it possible that the accuracy of the 10 MHz signal for both GPSDOs is more or less independent of the particular state of the phase at their given level of frequency accuracy? In other words, for either (and both GPSDOs) once the phase slips somewhere between 0 and 360 degrees the GPSDO is letting it slip such that it goes back to it's given frequency? Or said differently, the phase slippage for a single GPSDO is just jitter within one 1 Hz (or perhaps jitter within 1 milliHz or 1 microHz or 1 nanoHz or whatever the level of accuracy is that that GPSDO produces)?
And while this jitter bracketing is occurring with one GPSDO, the second GPSDO is doing it's own jitter bracketing within it's own level of accuracy - which could (if the two GPSDOs were identical with identical antenna feeds) be the same level of accuracy but nonetheless be out of phase with one another.
This last part doesn't seem so likely if the two GPSDO's were really identical including the antenna feed. Then they should have the same accuracy and same phase jitter, and the only question is did they startup/lock at the same time (perhaps unlikely) - but at least two identical GPSDOs with the same antenna signals should at least have their 10 MHz sine waves stay relative to one another. I think... maybe?
Trying to get my head around this. Thx
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Trying to get my head around this. Thx
Each source has its own noise. Parallel connection of several noise sources results in noise reduction by the root of N times.
It's simple for voltage sources. I don’t know how to parallelize the frequency sources.
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Hi,
my BG7TBL unit has a U-blox M8N GPS receiver. A least, on bootup, it says it is.
Just out of curiousity, I have replaced it with a U-blox M8T, which is the version for timing application.
It is just a 1:1 exchange, no hardware mods needed.
I did not make any changes in the U-box configuration and it works on the spot.
Unfortunately, I have no means of verifying, if this is really a useful modification.
As far as I remember, it has been done before.
Are there any useful adjustments of the chip settings via u-center?
Regards
Chris
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Very unlikely, as different makes / models will probably have different processing circuitry which will introduce slight time differences into the output paths. I have the three different GPSDOs mentioned above connected to a single external antenna via a splitter and identical cables, and they all differ marginally when compared against each other. With different GPSDOs you have to bear in mind that the signal received by any antenna is constantly changing due to atmospheric/tropospheric influences, and the firmware in each unit will have its own way of correcting the errors, so the outputs from each will always be slightly different by default.
But I'd say that long term the frequencies should match...
BTW: is there any solution / knowledge in which model of the BG7TBL GPSDO the frequency offset has been fixed and / or whether older models can be updated? I have a 2017 version and it shows a constant (average over 8 hours) offset versus a different GPSDO. The offset is in the ballpark of 2mHz (0.5ppb).
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You really put a 80€ module into an 80€ GPSDO?
Wow and i thought about the 25€ Neo-M9N if it is worth..
Unfortunally i have to replace the Atmega8A with new Software. Neo-9 wants to talk fast er than 9600baud..
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You really put a 80€ module into an 80€ GPSDO?
Wow and i thought about the 25€ Neo-M9N if it is worth..
Unfortunally i have to replace the Atmega8A with new Software. Neo-9 wants to talk fast er than 9600baud..
Yes, really!
It was a used module for like 16€. So that puts it somewhat in perspective.
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Are there more M8T for 16€ in your source?
Is it truly a genuine one? Found used ones in eBay but im concerned if they are still working / genuine. Would be easier than reprogramming the atmega8. Whats special about m8t vs m9n?
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Answer to myself... M8T has specified lower jitter..
EBay seller will auto accept for 15$..
Now i will get one and try..
I can save the "expensive" Neo-M9N for something which needs navigation..
Hopefully i will not kill the PCB this time first time was OK second time removing the module we will See..
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Answer to myself... M8T has specified lower jitter..
EBay seller will auto accept for 15$..
Now i will get one and try..
I can save the "expensive" Neo-M9N for something which needs navigation..
Hopefully i will not kill the PCB this time first time was OK second time removing the module we will See..
I got mine probably from the same seller.
They just cut the pcb with the module on it.
I did heat the pcb from the backside with hot air until the module just fell off.
I think, these are genuine modules from decomissioned commercial gear, which probably would not be equipped with fake ones.
To remove the module on the gpsdo, I used a tweezer type soldering iron with tips was wide as the module.
You need quite some heat.
It finally worked, but it was not really elegant and a risk always remains.
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I would like to buy myself a similar standard. But there are so many offers that I am at a loss.
Some sellers offer a choice of any two standards. Does it mean that they have a more modern receiver?
Is it right to choose the BDS + GALILEO combination as more modern and accurate?
Will I be able to switch the used standards myself?
I see a proposal with HP / Agilent 10811 OCXO inside. But there is no screen and no choice of GPS standards.
I heard that they have a small static error. Perhaps there are models where this problem is solved?
What else is worth paying attention to?
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AFAIK GPS has the most satellites in the sky and best coverage. Another thing to consider is that all these systems have a slightly different time source (based on country/region of origin) so they can (have to) drift a bit when compared to eachother. Perfect time doesn't exist; it is always an approximation.
The unit from BG7TBL is OK (but make sure you get at least a 2019 version). A couple of days ago I also ordered a unit based on a (surplus) Trimble GPSDO module to have a comparison.
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So the M8T arraived..
Had some trouble changing everything back..removed the cut out pcb with my hotair and a (not so good) little bump an my silicon mat... Shield fell off and a tiny tiny little antenna part (i think the antenna supply switch) in the module.. But i think i repaired it with a lot of flux and hotair. The module gets a fix pretty fast...)
But it looks like the module is working.
Unfortunally the genuine atmega8 is not accepting the UART output from m8t..
The atmel shows still ALM because something he expected is missing. Is it really working with the genuine atmega @ Ringmodulator ??
I connected it to ucenter to clean the SPI flash maybe there is still some old configuration but it looks like i cannot clean the configuration. It is also only using GPS and Glonass not Galileo vor Baidou and i can not enable them. Maybe i use the control Software wrong??
If i cannot get it to work with the old atmega i still have to rewrite the code..:-(
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My guess: Either you got an older version of the BG7TBL GPSDO, which has a different interface on the Atmega8 side or you got a chip clone. The problem could be an Ublox M8 clone from China, which is a common problem. Sometimes even the label does not match the chip underneath in terms of version. or variante. A missing flash memory might be an indication of this too. Those Ublox chip clones / fakes seem to be all over the place in Asia, looking the same from the outside and often carry a fake Ublox label too. Even Ublox has already reacted to this and has a note about this on their Swiss website. The clones (Ublox fakes) seem to differ internally regarding the chip version, features and precision (sometimes or often) but are available a lot cheaper to a potential buyer, thus a whole industry seems to have been focused on this. They seem to be working "OK" just navigating, but lack some advertised features. It might help to buy the originals (new) either from the manufacturer directly or from a well known supplier (Digikey, Mouser etc.) or used ones taken from a well known seller and source like Huawei modules. Ublox u-center software might be used to identify those clones because it will report an error if something is missing.
You will find several YouTube videos about those clones when looking specifically for it...
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Many of them are supposed to have an internal TCXO but don't have it. So they are less accurate -substantially less accurate than they should be.
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When reading through all the posts here in this thread and looking through the accompanying pictures I got the impression, that many BG7TBL GPSDO units don't have a "real" U-blox GPS chip installed but one of the many Chinese copies ("fakes") floating around on the Chinese internet. U-Blox themselves warns about this too, because they seem to have experienced the same when buying their own chips from some of the better known online market places or dealers in China. Seems to become a general and common problem nowadays. They name Ebay or AliExpress as one of the sources for this and have provided some exemplary samples for this taken from complaining users posts. Some dealers / "manufacturers" sold items, which had removed the label altogether, some have a fake label and some show a "compatible" but different chip family (and manufacturer) when looking at the init messages. Some even show false version labels, hiding an older chip version pretending to be a newer one. Other clones lack the standard flash chip or have an "original" U-blox GPS chip but the rest is of lower quality as the real thing. They usually sell for a lot less when bought this way. BG7TBL probably doesn't seem to care as long as they are functional one way or the other and has not provided any GPS chip specific information. :palm: |O
The problem for the uninformed Buyer seems to be, that there are so many copied / fake ones nowadays, that it is hard to tell them apart most of the time, when just looking at them from the outside or by opening the unit's housing. It seems to me, that buying only from U-blox directly (expensive) or one of the "official" resellers / distributors or trusted sources, when "used", will provide the needed security to get an "original" U-blox chip.
Are there any information available about replacing the "U-blox" GPS chip (old=>new), when one wants to be sure ?
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@burkm
First, BG7TBL is supposedly the name/callsign of an amateur radio operator who has designed many, many radio circuits - his GPSDO is just one of these designs.
But it seems BG7TBL is licensing his designs or getting them copied/pirated by a number of different companies, who all sell them under his "brand" BG7TBL. You can only tell them apart when you open them, and the differences are not immediately obvious.
I think worrying about real or fake u-blox GPS modules in a BG7TBL GPSDO bought on eBay, Amazon or AliExpress is somewhat missing the point: these are very cheap instruments that either work within specifications and satisfy your needs, or you should just return them to the seller and buy professional grade (and certainly more expen$ive) instruments.
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Just a short update i will give some more information later when im not so busy anymore.
The used M8T from eBay is working quite well. Even with the "original" still locked AVR.
The issue was that the GPS module must be configured the right way (NMEA stream must start with the right "talker ID" for GPS)
And it is not possible to enable more than 3 GNSS at once even if 4 are available..
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@burkm
First, BG7TBL is supposedly the name/callsign of an amateur radio operator who has designed many, many radio circuits - his GPSDO is just one of these designs.
But it seems BG7TBL is licensing his designs or getting them copied/pirated by a number of different companies, who all sell them under his "brand" BG7TBL. You can only tell them apart when you open them, and the differences are not immediately obvious.
I think worrying about real or fake u-blox GPS modules in a BG7TBL GPSDO bought on eBay, Amazon or AliExpress is somewhat missing the point: these are very cheap instruments that either work within specifications and satisfy your needs, or you should just return them to the seller and buy professional grade (and certainly more expen$ive) instruments.
Might be, but they are all sold under the call sign/name of BG7TBL and he probably is the designer (and manufacturer) of those units. I bought mine over the internet through one of the many ebay dealers. But when i contacted him by E-Mail some time ago he never mentioned any other manufacturer. The reason that I question the built-in GPS chips, because most of them available on the Chinese market are fakes or at least "clones". If you look closer at those photos provided here (GPSDO) and the labels going with it, it looks as if many clones/fakes are used in his designs / items too, probably because they are cheap to get. Information on those BG7TBL units are scares, one really doesn't know against what specs the units have to be validated except that the units are somehow "functional". Most of the buyers here don't question the labeled GPS chips, because they just trust, what is been shown, which might not be what they are getting.
I.e. my own unit had all label markings rubbed off except a small left upper hand section with the U-blox trade mark shown, thus no hint what version I got and if it's "real". The label was affixed somewhat slanted and off-center, which never seems to be the case with original units... 8)
If you look around for this on the internet there are lots of videos and articles about this, but - surprisingly - never mentioned / questioned here...
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Just a short update i will give some more information later when im not so busy anymore.
The used M8T from eBay is working quite well. Even with the "original" still locked AVR.
The issue was that the GPS module must be configured the right way (NMEA stream must start with the right "talker ID" for GPS)
And it is not possible to enable more than 3 GNSS at once even if 4 are available..
Actually in my experience: the M8T only allows certain combinations of maximum 3 different GNSS, 4 is impossible. Also, having 3 GNSS enabled at the same time is not necessarily a good idea when it comes to timing applications such as a GPSDO. I am using an M8T module with just two constellations enabled (which happens to be the default): GPS and GLONASS. But I suspect the timing pulse is derived only from the GPS constellation, in normal use. When I enabled the Galileo constellation, the M8T took much longer to get a fix - and to generate a stable PPS.
YMMV, of course.
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Anybody succeed to putting a “real” M8T into those units ? The reason I ask is the T family have diff pin out than the “N” or other family (real or fake) they are using.
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I put a real M8T into my unit. There is no other pinout. Just swapped the fake module to an used M8T from eBay and reconfigured in the right way. Everything works.
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Attached my final M8T configuration with 3 activated GNSS (GPS,GLONASS,Galileo)
Fix is quite fast I'm located in Germany so there is better Galileo coverage than Baidou..
(remove .hex)
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Attached my final M8T configuration with 3 activated GNSS (GPS,GLONASS,Galileo)
Fix is quite fast I'm located in Germany so there is better Galileo coverage than Baidou..
I would think changing the M8T settings from the factory default makes very little difference, the most important factor is really whether you have a good exterior antenna with an unobstructed view of the sky.
Also, from everything I have read: with a good exterior antenna a much cheaper M8N module works just as well as the M8T in a simple GPSDO design such as the BG7TBL
YMMV.
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You have to change the configuration to get it to work with the AVR in the E-GPSDO Designs..
M8T has builtin TCXO
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You have to change the configuration to get it to work with the AVR in the E-GPSDO Designs..
M8T has builtin TCXO
Yes, I know, but the TCXO in the M8T module makes no difference when the module is used in a GPSDO: it's the OCXO (and the performance of the control loop) in the GPSDO that matters.
For the BG7TBL GPSDO, I believe replacing the M8N with an M8T provides zero improvement in any measurable parameter, whether it's overall frequency stability, time to achieve satellite acquisition, frequency stability in holdover mode, etc.
Of course I would be glad to be proved wrong, if anybody has the numbers that clearly demonstrate an advantage for the M8T vs M8N in a BG7TBL.
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Really numbers i don't have.
My Counter is only the DG992 internal one or my SVA1032X but "subjective" wise i think there is less deviation / jitter since i upgraded to M8T in the "over time" statistics of the DG992 counter. With the fake Module there was more deviation / jitter . But i have also upgraded the antenna to an Beitan one which is "bigger" and has official support for / advertised for all 4 GNSS systems.
Less Jitter ist also advertised from the M8T Module and for 15$ it's a cost effective upgrade to a genuine one. So "it feels better / more trust worthy now" it's like the " placebo effect " you think it must be better now...
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Really numbers i don't have.
My Counter is only the DG992 internal one or my SVA1032X but "subjective" wise i think there is less deviation / jitter since i upgraded to M8T in the "over time" statistics of the DG992 counter. With the fake Module there was more deviation / jitter . But i have also upgraded the antenna to an Beitan one which is "bigger" and has official support for / advertised for all 4 GNSS systems.
Less Jitter ist also advertised from the M8T Module and for 15$ it's a cost effective upgrade to a genuine one. So "it feels better / more trust worthy now" it's like the " placebo effect " you think it must be better now...
Until now I never considered the bg7tbl gpsdo to have a fake Ublox module. But I have to say that compared to a GPSDO based on a real Ublox module and one from Trimble it looks like the bg7tbl is less stable (measured over 48 hours and using the exact same brand/model antennas). Maybe it is time to crack it open and check; if there is a fake uBlox inside I probably replace it with a real one.
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[attachimg=1]I just got a new BGTBL GNSSDO, the successor to the GPSDO, with an used (OEM-)specific OCXO (C-MAC 48S1164).
Just would like you to know, that the parts configuration and placement does and may vary depending on the original OCXOs used. This might make it almost "impossible" to replace a defective (original) OCXO with another one without adding additional parts of sometimes unknow specs, dependig what OCXO was used originally by BG7TBL. The major problem is, that there are no schematics "in the wild" or supplied, which could be used. The latest incarnation of the GPSDO, now called GNSSDO, has a new motherboard (2021-06-10) to adapt to all kinds of (used) OCXOs which might be available right now on the used market. Unfortunately many rare OEM OCXOs are not documented, even when searching the net intensively, and may feature - eventually - a different PIN layout or other variations in specs, which make it almost impossible to find a direct replacement in those cases. Mine i.e. got an OEM specific C-MAC OCXO, which seems to fluctuate quite heavily below the 10MHz mark, Unfortunately the OP-amp multiplier had been set to x3 by BG7TBL already, but my fully functional replacement OCXO (Oscilloquartz 8663-XS) does fit mechanically but not electrically exactly for this reason, because some parts are missing or are new on the board (solder pads are unpopulated, no values given etc.) for substituting the OCXO. Because of the missing parts no 10MHz signal is been produced, although the Oscilloquartz OCXO 8663-XS is fully functional as tested several times. I already looked around for another replacement OCXO (same kind), but no luck...
What makes me wonder is, that the label on the GPS-chip has been removed although it is supposed to be an "Ublox NEA M8N " as stated by the seller, which told me, that he had checked this himself with the Ublox control software. I will have to check this out later on too. Some Ublox clones identify themselvs as Ublox chips but dont have the corresponding flash on board as tested by others already.
Sending it back from Europe costs a lot too and does not make this feasible. Note: I will add some photos of the "new" board if I got the time to do it.
If you look at page 1 of this thread, you will find an ever changing list of different board layouts, which seems to continue "endlessly" up to the current date. Many OCXOs have an identical PIN layout and usage, but some vary quite a bit not only by size.
PS.: Latest units have become quite expensive for such a unit because they now reach about appr. €200 after importing them to Europe.
The factory installed solder bridge on the X3 pads have beeen already removed on the photo of the PCB.
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In the end an OCXO just needs a power supply and tuning voltage. It shouldn't be hard to retrace the circuit which drives the OCXO tuning voltage. Most likely a DAC and an opamp. Power supply is a matter of measuring which voltages are available where (likely 5V and 12V). And some retracing to determine where the filtering components are and then to move these if necessary. Only things you need to find out are a DMM with continuity and a piece of paper to draw on.
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My BG7TBL, (see my pictures earler in this thread) had a gps unit with the markings removed. It was detected by ucenter as an M8n.
It could be configured with ucenter and the bootmessage was als like a genuine device and it worked just fine So I am pretty convinced, that it was the real thing.
I have replaced it with a M8T which is pin compatibe. no further mods on the pcb needed.
Be aware, that there are Neo and Lea versions, that have different dimensions.
I have also replaced the OCXO with a Morion MV89A double oven.
It is not rocket sience.
Some info here http://amateurtele.com/index.php?artikel=203&hlk=en (http://amateurtele.com/index.php?artikel=203&hlk=en)
and here https://www.youtube.com/watch?v=gBkRFT9TgQI (https://www.youtube.com/watch?v=gBkRFT9TgQI)
All in all, I dont think, that these modifications are really worth the hassle and if I had nor tried, I would never have known.
Remember, not all BG7TBL gpsdos are created equal.
Chis
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I just got a new BGTBL GNSSDO, the successor to the GPSDO, with an used (OEM-)specific OCXO.
Just would like you to know, that the parts configuration and placement does and may vary depending on the original OCXOs used. This might make it almost "impossible" to replace a defective (original) OCXO with another one without adding additional parts of unknow specs, dependig what OCXO was used originally by BG7TBL. The major problem is, that there are no schematics "in the wild" or supplied, which could be used. The latest incarnation of the GPSDO, now called GNSSDO, has a new motherboard (2021-06-10) to adapt to all kinds of (used) OCXOs which might be available right now on the used market. Unfortunately many rare OEM OCXOs are not documented, even when searching the net intensively, and may feature - eventually - a different PIN layout or other variations in specs, which make it almost impossible to find a direct replacement in those cases. Mine i.e. got an OEM specific C-MAC OCXO, which seems to have reached (almost) "End-of-life" (tuning voltage 8.212 82VDC, multiplier is X3 already) but my fully functional replacement OCXO (Oscilloquartz 8663-XS) does fit mechanically but not electrically exactly for this reason, because some parts are missing on the board (solder pads are unpopulated, no values given etc.) for substituting the OCXO. I already looked around for another replacement OCXO (same kind), but no luck...
Sending it back from Europe costs a lot too and does not make this feasiblack boxle.
If you look at page 1 of this thread, you will find an ever changing list of different board layouts, which seems to continue "endlessly" up to the current date. Many OCXOs have an identical PIN layout and usage, but some vary quite a bit not only by size.
You have listed all the disadvantages related to the fact that the BG7TBL GPSDO is essentially a "black box" product. You don't have the schematics, it uses recycled and sometimes "unobtainium" parts, and you have zero control over the firmware. Its sole advantage is being extremely inexpensive for what it does.
If you want an Open Source (hardware and software) GPSDO that you can put together yourself for less than half the cost of a BG7TBL, and where you have total control of both the hardware and software, there are at least two described right here in the EEVblog forums:
1. Lars' DIY GPSDO by Lars Wilenius.
2. The STM32 GPSDO by yours truly i.e. myself.
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In the end an OCXO just needs a power supply and tuning voltage. It shouldn't be hard to retrace the circuit which drives the OCXO tuning voltage. Most likely a DAC and an opamp. Power supply is a matter of measuring which voltages are available where (likely 5V and 12V). And some retracing to determine where the filtering components are and then to move these if necessary. Only things you need to find out are a DMM with continuity and a piece of paper to draw on.
I tried this already myself, but the new PCB has a somewhat different layout (more complex) in comparison to older PCBs, which makes it near "impossible" to find corresponding parts, because they didn't exist before and are of unknow specs...
Some components with the same name have different values compared to older PCB editions. This makes it hard to tell, what should be used, when switching the OCXO. I don't want to exchange components on half the PCB after all without really knowing what I'm doing...
Note: Even the multiplier (x2, x3) seems to use differently specified components and is - componentwise (resistors) - partly unpopulated, although the OP amp used (358) is the same. Not even the operating voltage of the OCXO is specified on the label, thus I have to trust BG7TBL to have selected the right one. Note: Some of the C-MAC OCXOs have operating voltages of 12V, 15V and 24V.
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Many people here in this thread have been obsessed with swapping out the u-blox GPS module in their GPSDO for a much more expensive and supposedly more precise one, and supposedly that would make their BG7TBL GPSDO perform "better" or "more accurate".
Of course most people don't even have access to the equipment required to back these claims with solid data.
But one person (John Ackermann N8UR) went ahead and did a rather good job of collecting the data on a variety of u-blox receiver modules, and the verdict is quite clear imo. They all perform more or less the same.
https://hamsci.org/sites/default/files/publications/2020_TAPR_DCC/N8UR_GPS_Evaluation_August2020.pdf
A very good read, and perhaps that can settle the question.
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Many people here in this thread have been obsessed with swapping out the u-blox GPS module in their GPSDO for a much more expensive and supposedly more precise one, and supposedly that would make their BG7TBL GPSDO perform "better" or "more accurate".
Of course most people don't even have access to the equipment required to back these claims with solid data.
But one person (John Ackermann N8UR) went ahead and did a rather good job of collecting the data on a variety of u-blox receiver modules, and the verdict is quite clear imo. They all perform more or less the same.
https://hamsci.org/sites/default/files/publications/2020_TAPR_DCC/N8UR_GPS_Evaluation_August2020.pdf
A very good read, and perhaps that can settle the question.
Thats not 100% true. The F9 series is half an order of magnitude better.
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Many people here in this thread have been obsessed with swapping out the u-blox GPS module in their GPSDO for a much more expensive and supposedly more precise one, and supposedly that would make their BG7TBL GPSDO perform "better" or "more accurate".
Of course most people don't even have access to the equipment required to back these claims with solid data.
But one person (John Ackermann N8UR) went ahead and did a rather good job of collecting the data on a variety of u-blox receiver modules, and the verdict is quite clear imo. They all perform more or less the same.
https://hamsci.org/sites/default/files/publications/2020_TAPR_DCC/N8UR_GPS_Evaluation_August2020.pdf
A very good read, and perhaps that can settle the question.
Thats not 100% true. The F9 series is half an order of magnitude better.
"better"? That is a poor way to describe the data in the article. :palm:
Also, the "better" you refer to would make zero difference in a BG7TBL GPSDO. But I would be happy to be proved wrong, if you or anybody else have the data to show for it. :popcorn:
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The final question - for me - is: do any improvements of the GPS chip or OCXO provide either significant higher accruracy and/or stability of the generated 10 MHz signal, because that is the main purpose of my unit ?
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The final question - for me - is: do any improvements of the GPS chip or OCXO provide either significant higher accruracy and/or stability of the generated 10 MHz signal, because that is the main purpose of my unit ?
The output phase noise is determined mainly by the OCXO parameters. So choosing a better OCXO can give a noticeable improvement if a better one can be found.
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That seems to be my "problem" right now, because the BG7TBL installed C-MAC OEM-OCXO 48S1164 (DC1212=> December 2012) drifts slowly downward (constant voltage) or needs a slowly increasing voltage to keep its frequency constant. This - probably - seems to be the original reason, why the C-MAC (now Rakon) OCXO has been replaced so "early". My Oscilloquartz DOCXOs (8663-XS) perform much better with respect to frequency stability compared to the Oscilloquartz OCXOs. After searching the internet for some time now, I still didn't find any specific information about this C-MAC OCXO. The unusual size (50.84 mm both dimensions) and the pin-out seems to be a specialty of the C-MAC OCXO, because I found similar units only in a rather "old" C-MAC catalogue (2000) of this manufacturer.
Unfortunately BG7TBL had its multiplier already set to x3 probably because of this drift. During measuring the C-MAC OCXO it never actually reached the 10 MHz...
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The final question - for me - is: do any improvements of the GPS chip or OCXO provide either significant higher accruracy and/or stability of the generated 10 MHz signal, because that is the main purpose of my unit ?
GPS chip: no.
OCXO: exactly as MegaVolt wrote.
The output phase noise is determined mainly by the OCXO parameters. So choosing a better OCXO can give a noticeable improvement if a better one can be found.
Instead of "noticeable", I would say "measurable", but that of course entirely depends on what measurement apparatus you can get a hold of. And again: most people don't have access to instruments that can measure an OCXO's phase noise.
Just to give you an idea, here is the data for a Vectron OX-204 OCXO: "The OX–204 achieves a close in phase noise performance of −140dBc/Hz at the 10Hz offset with a phase noise floor of <-175dBc/Hz."
https://www.vectron.com/products/ocxo/ox-204.htm (https://www.vectron.com/products/ocxo/ox-204.htm)
To measure -140dBc/Hz phase noise you need rather expensive instruments. And if you have such expensive instruments at hand, I would guess you are probably not using a $150 BG7TBL GPSDO.
Btw even used inexpensive 10MHz 5V OCXOs such as the ones that can be found online are specified for −120dBc/Hz @ 10Hz phase noise and that too requires expensive instruments (that most of us cannot afford) to measure.
Finally, there is the matter of cost/benefit. A new OCXO with superior phase noise specifications will cost you more than the BG7TBL GPSDO itself - if you can buy it at all in single quantities. And it will have no measurable benefit for you, since you won't have the means to measure and compare the phase noise before/after.
That seems to be my "problem" right now, because the BG7TBL installed C-MAC OEM-OCXO 48S1164 (DC1212=> December 2012) drifts slowly downward (constant voltage) or needs a slowly increasing voltage to keep its frequency constant.
...
That is not phase noise, that is frequency drift. Either you are not waiting long enough for your GPSDO's operating temperature to stabilize, or you have a defective OCXO, or something else (e.g. temperature compensation, power supply, etc) is not working correctly, in which case you are better off just buying another "black box" GPSDO and hoping that it comes with a better OCXO and works within specs. Or you can build your own Open Source GPSDO for < 50€ and experiment with / improve on it as you see fit.
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And find that every single xtal in XO or OCXO or DOCXO have its ovn individual aging curve. And it is not drift in oven temp but just xtal itself is ageing.
And then. If some OCXO have aged example year(s) running all times and then someone cut power and keep it some time without power... after then turn on... it have retract and is dropped more or less far back to history on its aging curve... but now... it recover much more fast back to its original nominal aging curve... how long this fast recovery takes... just who knows but here one week is short time. Xtals have also random hops. Other things may be also that owen teperature drift slowly due to components aging/drifting.
It is whole world where is not any single constant, everything is jumping randomly, drifting and walking more or less. (been there done that)
If in GPSDO OCXO control voltage do not slowly rise or fall over weeks and months... I can tell it have problem. Even if DOCXO is "wolds best" it have aging curve and retract if stored without power.
It need remember that after new power on it looks like aging more fast... because it typically drives back to the original aging curve much faster than the original aging is. As told, time when it reach original aging curve is mostly unknown but after start long time used and long time cold stored OCXO this aging after new power up may be quite fast in first hours and days. (until it reach nearly this original aging)
There is one proposal. Do not turn OCXO off, keep it always constantly running. Days, weeks, months, years. After power off, wait enough time. There may exist more random jumps and "fast" return to its individual already reached aging curve after retract. ("fast" mean much much faster than original aging)
Many peoples have alarmed when second hand OCXO drift so fast after they start use it. If there is not other reasons still this aging retract alone can be surprisingly fast (related to normal long time aging after example 1 year run) in first hours and days. (naturally it can only look after Oven have reached full temperature equilibrium.
But then there is also some OCXO products what are not perfectly hermetically sealed, example models where is mechanical adjustment (even if they also have electrical tuning).
These theory and practice can find whi is interested about xtals and ocxo secrets... it also have mysteries what science today do not know exactly, many mysterious things in xtals. (and every xtal is finally just as individual as every human)
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If we are talking about GPSDO, OCXO aging has no effect on the output parameters.
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If we are talking about GPSDO, OCXO aging has no effect on the output parameters.
Exactly. Phase noise and other output parameters are not affected by OCXO aging.
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It need remember that after new power on it looks like aging more fast... because it typically drives back to the original aging curve much faster than the original aging is. As told, time when it reach original aging curve is mostly unknown but after start long time used and long time cold stored OCXO this aging after new power up may be quite fast in first hours and days. (until it reach nearly this original aging)
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In OCXO jargon this is called "retrace". And yes, OCXO aging is a complex phenomenon affected by various variables. I wouldn't worry too much about OCXO aging, though, because it is exactly for that reason that GPSDOs operate with a closed loop (either PLL or FLL or a hybrid PLL/FLL) to control the OCXO frequency.
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I did not talk about "phase noise", I did not even mention it (?)...
I talked abou frequency stability or drift, which I measured with my Rigol DM3688 DMM. Within 2 days (48h) the tuning voltage drifted (for almost constant frequency measured by my Fluke PM6685) from 5.24322 up to 5.24756 VDC. The runtime of the OCXO (GNSSDO) and Rigol DMM is currently more than 22 days without interruption. This would justify the x2 settings of the multiplier but it was already set for x3 by BG7TBL, which makes me wonder.
Accelerated retrace of a used OCXO should usually be finished after that period of time. I got an older version (BG7TBL GPSDO 2015-6-19), which retraced a lot faster after all, although the OCXO was correspondingly older.
May be there is someone here, who got a "standard" sized OCXO in his rather current BG7TBL GPSDO or GNSSDO, who has a higher resolution photo of the board, which I could use as a template for changing mine...
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...
Within 2 days (48h) the tuning voltage drifted (for almost constant frequency measured by my Fluke PM6685) from 5.24322 up to 5.24756 VDC.
...
That is way too little data to reach any conclusion. :-//
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...
It need remember that after new power on it looks like aging more fast... because it typically drives back to the original aging curve much faster than the original aging is. As told, time when it reach original aging curve is mostly unknown but after start long time used and long time cold stored OCXO this aging after new power up may be quite fast in first hours and days. (until it reach nearly this original aging)
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In OCXO jargon this is called "retrace". And yes, OCXO aging is a complex phenomenon affected by various variables. I wouldn't worry too much about OCXO aging, though, because it is exactly for that reason that GPSDOs operate with a closed loop (either PLL or FLL or a hybrid PLL/FLL) to control the OCXO frequency.
Yes as I told "Even if DOCXO is "wolds best" it have aging curve and retract if stored without power."
(I have used tens of years term retract independent of "Merriam-Webster")
And as you told it is norma, no need worry so much. But when someone wonder how it drift perhaps faster than he think is ok, reason may be this retract related phenomenon.
In cheap GPSDOs as example these many BG7TBL produced are, there is not so much what average user can do for optimize Discipline / LOOP parameters. As can do example in quite cheap old TrimbleThunderbolt and some others.
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Yes as I told "Even if DOCXO is "wolds best" it have aging curve and retract if stored without power."
(I have used tens of years term retract independent of "Merriam-Webster")
And as you told it is normal, no need worry so much. But when someone wonder how it drift perhaps faster than he think is ok, reason may be this retract related phenomenon.
I entirely agree with you.
In cheap GPSDOs as example these many BG7TBL produced are, there is not so much what average user can do for optimize Discipline / LOOP parameters. As can do example in quite cheap old TrimbleThunderbolt and some others.
Yes, in these "black box" GPSDOs the average user has zero control over the firmware, the PLL parameters, etc. These GPSDOs are inexpensive, but not designed to be hacked or serviced by the average user.
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...
Within 2 days (48h) the tuning voltage drifted (for almost constant frequency measured by my Fluke PM6685) from 5.24322 up to 5.24756 VDC.
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And problem is?
It is its work, keep OCXO output "roughly" *) around 10MHz, it need discipline and 2 days... perhaps just after turn on, if so, it is totally nonsense and totally lack of enough data for anything.
Keep least one month constantly on or more... then you can see just bit some kind of curve how it goes and also perhaps some less change later.
Just look/watch it example using Lady Heather (yes full use of it may need some experience, its UI is bit garbled), you get all trends etc how it goes.
*) yes I mean really just quite roughly.
But I am retired time nutter so it is better than I stop before I even start. ;)
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The tuning voltage of the OCXO after 3 days of measurements (this morning) has now reached 5.24963 VDC as shown by my labs DMM. The unit itself is up and running continously for almost 23 days already as stated before...
I checked the frequency output of the "new" BG7TBL GNSSDO frequently during that period (22-days +) and both displays (Fluke PM6685 + external star 4+ ATDC ref. freq. and the built-in LCD-display) - always - show frequencies below 10 MHz, which made me wonder, because the shown frequencies by my other GPSDOs usually "oscillated" around 10 MHz during that "startup" period (more or less), when arrived, after a few days run-time. Even my older BG7TBL GPSDO from 2015 provided a much "better" stability and accuracy measured by the instruments I got. I contacted the seller already in China by e-mail but got no satifying answer from him, because he refered me to BG7TBL.
I relate those experienced differences to the C-MAC OCXO installed in the "new" GNSSDO. This was the main reason for wanting to exchange the installed OCXO against one of those Oscilloquartz 8662-XS I got, which show a date code of "08/47" and which seemed to be much more stable after only several hours of runtime than the one installed, judging by the oscilloscope i hooked up to it. But due to the new and only partly populated PCB I have not been able to do this for various reasons.
How long would you expect me to wait for the OCXO to stabilize during retracing ? 30 days, 40 days or even more ???
I wonder how those units and their OCXOs have been tested by BG7TBL, if reaching stability of the OCXO will take that long ...
What made me wonder too, that the tuning voltage multiplier was set for "x3" right from the beginning although current measurements (see above) show only a need for "x2" including some proper headroom as a reserve.
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I have been following various GPSDO threads for quite a while now, and I'd like to ask, what do people use their GPSDO for? It seems to me there are two groups, those that play with them, trying to make them 'better'. And those that use the GPSDO as their primary reference. Is the bg7tbl useful for either of these purposes? From this thread, it seems the bg7tbl is a changing object, so people buying it as a primary reference have no idea of what they are buying and cannot rely on tests by others because they are all different. And those that play have much better equipment and it seems pointless to try modifying a cheap box when they already have a better standard. Since I am close to finishing my GPSDO design, it would be interesting to know who, if anyone, would use it, and for what.
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cheap primary reference that is good enough.
it doesn't satisfy the level of time-nuts and volt-nuts metrology obsessions, but it's far beyond the requirements of almost any casual hobbyist. after all, most hobbyists don't even have a frequency reference at all.
if someone comes up with a better, cheaper gpsdo solution than bg7tbl, they should easily be able to take over the market for such devices.
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cheap primary reference that is good enough.
it doesn't satisfy the level of time-nuts and volt-nuts metrology obsessions, but it's far beyond the requirements of almost any casual hobbyist. after all, most hobbyists don't even have a frequency reference at all.
if someone comes up with a better, cheaper gpsdo solution than bg7tbl, they should easily be able to take over the market for such devices.
Well I think that is what I am trying to achieve. I don't know about better, as I pointed out there are many bg7tbl versions. However, I am working on cheaper. My design criteria is to achieve a 10MHz output +-0.01Hz and be able to verify it. I am working on the idea that some people would do some construction, so the design is BYO power, BYO GPS module, BYO case. The actual GPSDO board I think can be populated for under AU$20. So far, it is all working and I am writing it up here (https://www.eevblog.com/forum/projects/budget-gpsdo-a-work-in-progress/msg3481886/#msg3481886). The first attempt at a PCB board has been produced and I am waiting for it to arrive.
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i think most people buying bg7tbl aren't looking for BYO DIY. they want something inexpensive that you plug in and it works. at least that's why i bought mine.
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My point of view is, that anything, i.e. a GPSDO or GNSSDO, must - at least - fulfill the manufacturer or seller provided "official" specs, because that is the main reason I am buying something. Sometimes even a 2nd time lateron, if something has changed in a - for me - relevant matter. Others seem to share this view, because they are "testing" what they got. If a seller gives a clear answer to a provided question, this is at least what I want to be delivered, when I receive the item bought.
I don't care about "improving" something, which follows the data sheet already, because this depends on so many - mostly unknow - data, that I wouldn't / couldn't care about it.
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Until I brought my 'first' Frequency counter and had a fairly average Signal Generator at the time I 'needed' a reliable reference to set the counter and know how far the Feelcrud was off from what it showed. That was a much better Generator and several more Counters ago now >:D
The reality is that most users have about Zero need for a GPSDO and if it wasn't for the 10Meg gitter of the UBlox then one of these would do fine for 95-98% of us as a sort of ok reference. If all we need is a way to set another device then a 5:4 Lissajous with the UBlox supplying an 8Meg against an unknown near 10Meg device would get the job done for just a few $.
This does not in anyway apply to Time Nuts or those who have a need for sub Hertz resolution but the reality is that is the nerdy fringe (I aspire to this :-DD )
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I don't think, that I (or anyone) should judge any user by his "needs", because I don't know them and wouldn't dare to extrapolate this from the "outside"... 8)
For what reason he has bought it, is not to be decided by myself...
But he should get, what has been "promised" for the advertised items, at least not less.
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just an obvious question...
how is the GPS sync done
. by phase as PLL
. by frequency compare
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As far as i have concluded from several threads about the BG7TBL GPSDO / GNSSDO, it is done by PLL.
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As far as i have concluded from several threads about the BG7TBL GPSDO / GNSSDO, it is done by PLL.
At what freq. runs the PLL .. ?
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I have a version of this labeled 2019-08-09 on the case. I bought it back in late 2019 or early 2020, but I had a cross-country move and didn't get around to playing with it until now. I can confirm that the PPS signal is 3.3V. The serial on this board uses a 3.5mm audio jack, with TX on tip and RX on ring. The serial doesn't seem to output NUMA. I have tried three serial adapters. One is DB9 to USB, presumably tolerant of +/- 12V "true" RS232. Another just has 4 pins to USB, 3.3/5V serial. Finally, I tried the UART0 on my Raspberry Pi. The first two adapters report nothing (so probably something wrong with my cable) but using a different cable with the RPi UART, I get a stream of binary nonsense every second, about 5120 bytes per transfer, at 9600 baud. None of the other baud rates I tried did any better. The GPSDO otherwise behaves normally. It boots with PWR flashing and ALRM lit, then goes to both solid, then just PWR green solid after a few minutes of running.
Here's a hex dump of the data that I'm reading.
00000000: 3c0e cece 3ece cef0 cef0 8c30 3ef0 fef0 <...>......0>...
00000010: fef0 3ef0 ce0c 8cc0 3e3e f0fe f0fe 308c ..>.....>>....0.
00000020: cc30 0ef0 cec0 cef0 ce0e 3c3e 3ece 0e0e .0........<>>...
00000030: f00e f0fe 80fc 303e ce30 fef0 fec0 fc0c ......0>.0......
00000040: cef0 fec0 3e3e 3e3e f00c f0ce 0e0e f0fe ....>>>>........
00000050: 300e cefc 30fe f03e 3efe f0ce f03e f0fc 0...0..>>....>..
00000060: 30fe 30fe f0ce 0efe f0ce 803c f0ce f0fe 0.0........<....
00000070: 30fe 30fe 30fc fcce ce3e 30fe c0ce f03e 0.0.0....>0....>
00000080: fcfc 3c0e cece 3ece fece ce80 8c30 fe30 ..<...>......0.0
00000090: fece ce30 fe30 8cf0 ce30 fef0 3e3e fef0 ...0.0...0..>>..
000000a0: cef0 3cf0 fe30 3ece 30fe f03c 3c3e fef0 ..<..0>.0..<<>..
000000b0: 0ef0 fe30 0e3e fc30 fefe cece 3e3e cef0 ...0.>.0....>>..
000000c0: cef0 3cfe fe3e 0ece ce0e 8c80 cefe ce30 ..<..>.........0
000000d0: 3ef0 fef0 fef0 3cf0 ce0e cec0 3e3e f0fe >.....<.....>>..
000000e0: f0fc 300e f0ce c0ce f0ce 0e3c 3e3e ce0e ..0........<>>..
000000f0: 0ef0 0ef0 fe80 fc30 3ece 30fe f0fe c0fc .......0>.0.....
00000100: 0cce f0fe c03e 3e3e 3ef0 0cf0 ce0e 0ef0 .....>>>>.......
00000110: fe30 0ece fe30 3cf0 fe30 fef0 cec0 fe30 .0...0<..0.....0
00000120: 8cf0 3e3e 3efe f0fe 303e f03c f0fe 0e3e ..>>>...0>.<...>
00000130: 3ef0 fe30 8cf0 cc30 ce30 0ef0 0ef0 3e3c >..0...0.0....><
00000140: f0f0 fe30 cef0 ce30 fe30 fef0 fcf0 fef0 ...0...0.0......
00000150: fef0 3ece 3ef0 3ccc 0e3e fefe 3e0e ce8c ..>.>.<..>..>...
00000160: 0cce f0ce cece 30ce ce30 0cf0 fe30 cef0 ......0..0...0..
00000170: fec0 fe30 3cf0 0ef0 fe30 cef0 ce0e fe30 ...0<....0.....0
00000180: 3cf0 fe0e fe30 ce0e cef0 fc30 cef0 fef0 <....0.....0....
00000190: fe30 cef0 0ef0 fc30 fe0e 3ef0 fe30 0ef0 .0.....0..>..0..
000001a0: 3ef0 fc30 fe30 fe30 fe30 3ef0 3c3c 0e3e >..0.0.0.0>.<<.>
000001b0: f0fe 30ce f03e 3c3c fef0 fe30 3ef0 3e3e ..0..><<...0>.>>
000001c0: fcf0 fc0e 3ece fef0 fec0 cef0 3cfc fe3e ....>.......<..>
000001d0: 0ece ce0e cef0 8c3c cefe 30fe 0efe 30ce .......<..0...0.
000001e0: f0fc 30ce f00e f0fe 30fe f0ce 0efc 30fe ..0.....0.....0.
000001f0: f0ce 0efe 30fe f0ce 800c f0fe 30fe 30fe ....0.......0.0.
00000200: f0fe c0fc 30fe f03e f0fe 300e f03e f0fc ....0..>..0..>..
00000210: 0cfe 30fe 30ce f0fe f0fe 30fc 0e3e f0fe ..0.0.....0..>..
00000220: 300e f0fe f08c f0fe 303e f0ce 0efe 30ce 0.......0>....0.
00000230: f00c f0fe 30fe f0fe c0fe 30fc f0fe 0e0e ....0.....0.....
00000240: f0fe 30fe f0fe c03c cc0e f0fe c0ce f03e ..0....<.......>
00000250: fefe 3c0c cece 0ece f0ce 3ece fc30 fe0e ..<.......>..0..
00000260: fe30 3ef0 fe30 cef0 0cf0 fe30 cef0 ce0e .0>..0.....0....
00000270: fe30 0ef0 3cf0 fe30 fef0 ce0e 0ef0 fc30 .0..<..0.......0
00000280: 3ef0 cef0 fe30 cef0 fe80 fc30 3ef0 fec0 >....0.....0>...
00000290: fe30 cef0 0cf0 3ef0 fe30 0ef0 3ef0 fe30 .0....>..0..>..0
000002a0: 3cf0 0ef0 fe30 3ef0 cec0 fe30 0cf0 ce0e <....0>....0....
000002b0: fef0 fe30 3ef0 fc80 fe30 3ef0 fe0e fe30 ...0>....0>....0
000002c0: fe0c 8cc0 fe30 cef0 cef0 fef0 fc30 0ef0 .....0.......0..
000002d0: 3ef0 3ece 0ef0 0ef0 8cf0 3efe fe3e 0ece >.>.......>..>..
000002e0: ce0e 8cf0 ce3e cefe 30fe 0efe 300c f0fe .....>..0...0...
000002f0: 30ce f00e f0fe 303e f00c f0fe 303e f0fe 0.....0>....0>..
00000300: f0fe 303e f0cc c0fe c0fe 303e f00e f0fc ..0>......0>....
00000310: 300e f03e f0fe 303e f03e f0fc 303e f00e 0..>..0>.>..0>..
00000320: f03e f0fe 303c f0ce 0efe 30fe 0e3e f0fe .>..0<....0..>..
00000330: 303c f0ce 0efe 303e f00e f0fe 80fc 300e 0<....0>......0.
00000340: f0fe f0fe 30fe 0efc 80fe 303e f0fe c0fe ....0.....0>....
00000350: 303e f00c f0fe 0efe 300e f0ce f03e 8c0c 0>......0....>..
00000360: f03e f0ce f03e fefe 3e0c cece 0ece f0ce .>...>..>.......
00000370: 3ece fe30 fc0e fe30 fe0e fe30 cef0 0cf0 >..0...0...0....
00000380: fe30 ce0e cef0 fe30 0ef0 8cc0 fe30 3ef0 .0.....0.....0>.
00000390: cef0 fe0e fe30 0cf0 3ef0 3ece fe0e 0ef0 .....0..>.>.....
000003a0: 8cf0 3efe fe3e 0ece ce0e 8cf0 cef0 ce30 ..>..>.........0
000003b0: 0ef0 cec0 cef0 cc0e 3e3e 3ece 0e0e f00c ........>>>.....
000003c0: f0fe c0fe 303e ce30 fef0 fcc0 fe0e cef0 ....0>.0........
000003d0: fec0 3e3e 3c3e f00e f0ce 0e0e f0fe 300c ..>><>........0.
000003e0: cefe 303e f0fe f0fe f03e f0cc 0ece c03e ..0>.....>.....>
000003f0: 3ef0 fef0 fc30 cece 30fe fece ce3e c0f0 >....0..0....>..
00000400: 0cce 0e3e fe00 3e0e 8cce 3ece cef0 cef0 ...>..>...>.....
00000410: ce30 3cf0 fef0 fef0 0ef0 fef0 fef0 3c3e .0<...........<>
00000420: f0fe f0fe 30ce ce30 0cf0 cec0 cef0 ce0e ....0..0........
00000430: 3e3c 3cce 0e0e f0fe c0fe f0fe 303c ce30 ><<.........0<.0
00000440: fef0 fec0 fe0e 8cf0 fec0 3e3e 3e3e f00e ..........>>>>..
00000450: f08c 0c3e f0fe 300e cefe 30fe f03c 3ef0 ...>..0...0..<>.
00000460: 3ef0 ce0e fe30 fc30 fef0 ce0e fef0 cec0 >....0.0........
00000470: 3ef0 8cf0 fe30 fe30 fe30 fefe ce8c 3c30 >....0.0.0....<0
00000480: 3ef0 cef0 3efe fe3e 0cce ce3e cefe cece >...>..>...>....
00000490: c0ce 30fc 30fe cece 30fe 30ce f0ce 30fe ..0.0...0.0...0.
000004a0: f03e 3ef0 3ef0 ce0e fc30 3ece 30fe f03e .>>.>....0>.0..>
000004b0: 3efc f03c f0fe f0fe 300e 3efe 30fc fcce >..<....0.>.0...
000004c0: ce3e 3e3e f0ce f03e fcfc 3e0e cece 0ece .>>>...>..>.....
000004d0: c0ce fccc 303e f0fe f0fe f00e f0fc f0fe ....0>..........
000004e0: f03e 3ef0 fef0 fe30 0cf0 cec0 cef0 ce0e .>>....0........
000004f0: 3e3e 3cce 0e0e f0fe c0fe f0fe 303c ce30 >><.........0<.0
00000500: fef0 fec0 fe0e cef0 fcc0 3e3e 3e3e f00e ..........>>>>..
00000510: f08c 0c3e f0fe 300e cefe 303e f0fc 30fe ...>..0...0>..0.
00000520: f0ce c0fe 30ce f03c 3c3e fef0 fe30 3ef0 ....0..<<>...0>.
00000530: 3ef0 0cf0 3e3e c0fe 30ce f0ce 308c 300e >...>>..0...0.0.
00000540: f00e f03e 3ef0 f0fc 30ce f0ce 30fe 30fe ...>>...0...0.0.
00000550: f0fe f0fc f0fe f03e ce3e f03e ce0c 3cfe .......>.>.>..<.
00000560: fe3e 0ece ce0e 8cf0 ccce ce30 cece 300e .>.........0..0.
00000570: f0fc 30ce f0fe c0fe 303e f00c f0fe 30ce ..0.....0>....0.
00000580: f0ce 0efe 303e f0fc 0cfe 30ce 0ece f0fe ....0>....0.....
00000590: 30ce f0fc f0fe 30ce f00e f0fe 30fc 0c3e 0.....0.....0..>
000005a0: f0fe 300e f03e f0fe 30fc 30fe 30fe 303e ..0..>..0.0.0.0>
000005b0: f03e 3e0c 3cf0 fe30 cef0 3e3e 3efc f0fe .>>.<..0..>>>...
000005c0: 303e f03e 3efe f0fe 0c3c cefe f0fe c0ce 0>.>>....<......
000005d0: f03e fefc 3c0e cece 0ece f0ce 3e8c fc30 .>..<.......>..0
000005e0: fe0e fe30 cef0 fe30 cef0 0cf0 fe30 fef0 ...0...0.....0..
000005f0: ce0e fe30 fcf0 ce0e fe30 fef0 cec0 0ef0 ...0.....0......
00000600: fc30 fe30 fef0 fec0 fe30 fef0 3cf0 fe30 .0.0.....0..<..0
00000610: 0ef0 3ef0 fe0e fc30 fe30 cef0 fef0 fe30 ..>....0.0.....0
00000620: fe0c 3cf0 fe30 0ef0 fef0 cef0 fc30 3ef0 ..<..0.......0>.
00000630: ce0e fe30 cef0 0ef0 fc30 fef0 fec0 fe30 ...0.....0.....0
00000640: fef0 fe0c 0cf0 fe30 fef0 fec0 3ece 0cf0 .......0....>...
00000650: fec0 cef0 3efe fe3e 0e8c ce0e cef0 ce3e ....>..>.......>
00000660: cefe 30fc 0cfe 303e f0fe 30ce f00e f0fc ..0...0>..0.....
00000670: 30ce f0ce 0efe 300e f03e f0fc 30fe f0ce 0.....0..>..0...
00000680: 0e0e f0fe 303c f0ce f0fe 30ce f0fe c0fe ....0<....0.....
00000690: 303c f0fe c0fe 30ce f00e f03e f0fc 300e 0<....0....>..0.
000006a0: f03e f0fe 303e f00c f0fe 303e f0ce c0fe .>..0>....0>....
000006b0: 300e f08c 0efe f0fe 303e f0fe c0fc 303e 0.......0>....0>
000006c0: f0fe 0efe 30fe 0ece c0fc 30ce f0ce f0fe ....0.....0.....
000006d0: f0fe 300e f03c f03e ce0e f00e f0ce f03c ..0..<.>.......<
000006e0: fcfe 3e0e cece 0ece f08c 3cce fe30 fe0e ..>.......<..0..
000006f0: fe30 0ef0 fe30 ccf0 0ef0 fe30 3ef0 0ef0 .0...0.....0>...
00000700: fc30 3ef0 fef0 fe30 3ef0 ce80 fcc0 fe30 .0>....0>......0
00000710: 3ef0 0ef0 fe30 0cf0 3ef0 fe30 3ef0 3ef0 >....0..>..0>.>.
00000720: fe30 3cf0 0ef0 3ef0 fe30 3ef0 fe0c fc30 .0<...>..0>....0
00000730: fe0e 3ef0 fe30 3ef0 8c0c fe30 3ef0 0ef0 ..>..0>....0>...
00000740: fec0 fe30 0cf0 cef0 fe30 fe0e fec0 fe30 ...0.....0.....0
00000750: 3cf0 fec0 fe30 3ef0 0ef0 fc0c fe30 0ef0 <....0>......0..
00000760: fef0 3ece 0ef0 0cf0 cef0 3efe fe3e 0ece ..>.......>..>..
00000770: 8c0e cef0 ce3e cefe 30fe 0efc 30fe 0efe .....>..0...0...
00000780: 30ce f00e f0fe 30cc 0ece f0fe 300e f0ce 0.....0.....0...
00000790: c0fc 303e f0ce f0fe 0efe 300e f03c f03e ..0>......0..<.>
000007a0: cefe 0e0e f0ce f03c fcfc 3e0e cece 0ece .......<..>.....
000007b0: f08c f0ce 300e f0ce c0ce f0ce 0c3c 3e3e ....0........<>>
000007c0: ce0e 0ef0 fec0 fcf0 fe30 3ece 30fe f0fe .........0>.0...
000007d0: 80fc 0cce f0fe c03e 3e3e 3ef0 0cf0 ce0e .......>>>>.....
000007e0: 3ef0 fe30 0ece fc30 3ef0 fef0 fef0 0ef0 >..0...0>.......
000007f0: fef0 fcf0 3e3e f0fe f0fe 308c cc30 fefe ....>>....0..0..
00000800: cece 3ec0 f00e f08c f03e fe00 3e0e cece ..>......>..>...
00000810: 3c8c cef0 cef0 ce30 3ef0 fef0 fcf0 0ef0 <......0>.......
00000820: fef0 cef0 3e3e f0fc f0fe 30ce ce30 0ef0 ....>>....0..0..
00000830: 8cc0 cef0 ce0e 3e3e 3ece 0c0c f0fe c0fe ......>>>.......
00000840: f0fe 303e ce30 fef0 fec0 fe0e cef0 fec0 ..0>.0..........
00000850: 3c3e 3e3e f00e f0ce 0e0e f0fc 300e cefe <>>>........0...
00000860: 30fe f03e 3ef0 fe0e ce0e fe30 fe30 fef0 0..>>......0.0..
00000870: 8c0c fef0 cec0 3ef0 cef0 fe30 fc30 fe30 ......>....0.0.0
00000880: fefe cece 3e30 fcf0 cef0 3efe fe3e 0ece ....>0....>..>..
00000890: 8c3c cefe cece c0ce 30fe 30fc 8ccc 30fe .<......0.0...0.
000008a0: 30ce f0ce 30fe f03c 3ef0 fe0e ce0e fe30 0...0..<>......0
000008b0: 3e8c 30fe f03e 3ef0 fec0 0cf0 fe30 0e3e >.0..>>......0.>
000008c0: fe30 fefe cece 3c3c 0ece 0e3e fefe 3e0e .0....<<...>..>.
000008d0: 8cce 0ece c0ce fece 303c f0fe f0fe f00e ........0<......
000008e0: f0fe f0ce f03c 3ef0 fef0 fe30 0ef0 8c80 .....<>....0....
000008f0: cef0 ce0e 3e3e 3ece 0e0c f0fe c0fe f0fe ....>>>.........
00000900: 303e ce30 fcf0 fec0 fe0e cef0 fec0 3c3c 0>.0..........<<
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-
I get a stream of binary nonsense every second, about 5120 bytes per transfer, at 9600 baud.
There is something wrong here. The rule of thumb is 1 character for every 10 baud (1 start bit, 8 data bits, 1 stop bit). So should only get a maximum of 960 characters/second. Maybe the receiver has the ability to detect the baud rate and is locking onto the wrong rate.
Are you setting the receiver right. 1 start bit, 8 data bits, 1 stop bit, no control signals usually works.
There is a difference between RS232 and TTL. RS232 a 1 is -ve and a 0 is +ve. TTL a 1 is +ve and a 0 is 0. So the levels are opposite and are not interchangeable. Also a true RS232 receiver should not recognise a 0V signal, to have an active idle line there should be a 0 logic level, i.e. greater than +3V.
I have used the TTL to USB converters. They do require the right driver, make sure it works before attaching it to a circuit. You can do that by connecting the TX and RX lines and use a terminal program like PuTTY. If typed characters are echoed back it is working OK. I have had dodgy connectors provided with some converters.
The RPi receiver looks to be running at a much higher rate than the data. I am basing that on the hex received. The majority have adjacent 1s and adjacent 0s. 3c=00111100 ce=11001110 etc. But that's a guess.
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Just some feedback from my "incarnation" of the latest BG7TBL GNSSDO (no front date), which has been delivered "brand new" on August 5th 2021, PCB version 2021-06-10, software version "20191001". After > 30 days of uninterrupted run-time (possible OCXO retrace, but "stable" for the last 14 days) it has a documented deviation (Fluke high resolution counter PM6685 + external 10MHz star 4+ ATDC reference) of ~ -0.0244Hz which is a rather "large" compared to the promised max. deviation of 0.0002Hz (2E-11). Even the built-in LCD-display shows a similar value below 10 MHz !
A roof top mounted - active - timing antenna + GPS splitter delivers the GPS/GNSS signal of the supported satellite networks. The installed GPS chip is unlabeled (?) and supposed to be an Ublox Neo-8M (seller satement), which I didn't check yet. Antenna voltage had already been set to 5VDC by BG7TBL.
The built-in (OEM-)OCXO 48S1164 is (probably) made by C-MAC (now Rakon), date code December 2012, of rather "unusual" size (50.8x50.8x24mm) and pin out, wich seems to be "similar" to a Trimble OCXO etc. I couldn't find any specific information for it on the internet and it - unfortunatelly - can't be replaced easily (i.e Oscilloquartz 8663-XS, standardized), because of the form factor and pin out. Additionally the PCB itself is only populated (componentwise) for this built-in OCXO. The tuning voltage amplification factor had already been set (solder bridge) by BG7TBL to "x3". As measured, the OCXO could actually reach 10 MHz at 5.245 VDC but the supplied hardware and/or software algorithm won't let it (see above) for unknown reasons, staying always below this value, which is responsible for the given deviation.
After some lengthy conversation over the last 30 days (and raising a "conflict" through PayPal) the seller promised now to sent a "new unit", which is supposed to be working as stated by the "official" specs.
I will keep you up-to-date, after it arrives...
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Nearly two months ago, :horse:
@burkm
...
I think worrying about real or fake u-blox GPS modules in a BG7TBL GPSDO bought on eBay, Amazon or AliExpress is somewhat missing the point: these are very cheap instruments that either work within specifications and satisfy your needs, or you should just return them to the seller and buy professional grade (and certainly more expen$ive) instruments.
Now:
...
After some lengthy conversation over the last 30 days (and raising a "conflict" through PayPal) the seller promised now to sent a "new unit", which is supposed to be working as stated by the "official" specs.
I will keep you up-to-date, after it arrives...
So you roll the dice again and the saga continues... :popcorn:
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The seller decided to sent a new unit several days ago because of the stated problems. Hopefully I get more lucky this time. Tracking ID has been provided...
I don't know, what will happen with the import tax and customs fees etc. because he did sent it "free of charge". Will see, what the customs office will do about it...
Note: I wasn't sure, where my conflict (PayPal) will take me, because this would take some time for a response of the seller, contacting Ebay and a final decision abou a full or partial refund. Ebay refuses to tackle it as usual, after I checked with their help line, because of separation from PayPal.
Sending back "defective" unit to China from over here is relatively expensive because of high logistics costs, getting back the already charged/paid import taxes and fees from the customs department is truly laborious over here.
This would have to be deducted anyways from the price already paid to the seller too.
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The replacement unit seems to have reached the German customs a few days ago. I'm waiting for the delivery now...
I'm eager to know, how the German customs will handle the replacement, because the replacement unit has not been charged by the seller. An invoice and customs statement of the seller should list 0,0 cost.
Another question will be, how the replacement unit will handle the task and if it will hold the stated specs.
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After looking up the tracking info of the package, I discovered, that the provided tracking-ID of the replacement unit seems to point somewhere else but not my address, because the tracking info shows a different city now. I called DHL Germany about the whereabouts of my package, whose tracking-ID had been provided by the seller flyxy2015 on ebay. The lady from the DHL customer service told me (to my surprise), that the tracking ID belongs to a completely different customer in a different city in Germany. Seems that the seller flyxy2015 had probably provided an existent but "fake" tracking ID based on my previous complains, knowing, that China is far away...
I contacted the seller flyxy2015 by the ebay messaging system today again and asked about the "real" tracking ID of my package, but after looking casually around on the internet, it seems, that the seller flyxy2015 has been known already before as a cheater on those things like the tracking ID in case of complaints. Thus it would surprise me, if I would get any answer from the seller. Unfortunately the 60 days period has passed already on ebay, so I can't leave any negative comments about this behavior. Probably the actual intent of the seller...
So I suggest, that anyone, who reads this, is staying away from this seller.
If any further news will show up, I will post here.
Fortunately PayPal seems to be of some help in this situation, so not everything is lost :)
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I got a response from flyxy2015, that he will contact the post office to look for the sent package 8) and would sent another one :rant: :-DD
Strangly enough, because the German post (DHL) had told me already, that the provided tracking-ID did belong to a different person. Notwithstanding this response flyxy2015 told me, that he would to resend the package "soon". In the meantime I contacted ebay about this scam. If this will help, I don't know.
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Just got a new tracking-ID from flyxy2015, which is supposed to be for my address. Checking its destination, its been sent - again - to a completely different address: city and postal code over here.
Today I also got a letter from DHL Germany, which responded - in writing - to my original search request and told me, that the sent package in question had been redirected to the local post office (different adressee, different city and different location all together), because nobody was present at the original delivery address. Within the provided holding period the package has been picked up by the recipient, adifferent person. This was certainly not me, because the destination address provided by the sender was located elsewhere in Germany and does not correspond to my home address.
Strange things seem to happen...
My belief: flyxy2015 is trying to cheat on me, again. Thus beware ! :box:
I think this story is over now as been told...
PS.: Interesting. flyxy2015 has changed (at least partly) its current name for Ebay offers (Germany ?) to => elecdesign2015
if anything "new" comes up, I will post here...
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I confronted the seller with the findings through the ebay messaging system, that his provided "new" tracking-ID for me was sent (again) to a completely different address (and probably addressee), but he did not respond / react at all, just complete "silence"...
PS.: In the meantime the 2nd package / item has been delivered and (again) signed by the "real" addressee (different city, different address, different person), so its evident, that any warranty is non-existent, a replacement unit will never reach you, even if "promised" by the seller flyxy2015 / elecdesign2015 :wtf:
Note: Unfortunately the ebay comment period has expired in the (long) meantime, which seems to be the whole purpose behind these actions as reported by others too. Thus his "positive rating" stays untouched by those unpleseant experiences.
I contacted ebay Germany about this, but earned only shrugs about this. Earned money seems to count more for them...
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Just had a casual look at my "new" (3 month old) BG7TBL GNSSDO + Display unit. After 3 Month of beeing connected continously to the power supply and GPS antenna, the built in LCD-Display shows a value (2nd line) of "9 10 MHz -0.0243 Hz", far off the stated specs. The "9" does seem to show, that it is off spec, but my other BG7TBL GPSDO unit just works (almost ?) perfectly (12-digit + overflow Fluke PM6685 counter). The oscilloscope shows a right shifting signal compared to the star 4+ version I got. Both are connected actively to a single GPS timing antenna on top of the roof with almost free "hemispheric" sight of the sky by a GPS splitter.
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Lot's of sources , looked getting a while back , looking at getting again - but same issue - too many sources .
Did lots of searches [ must be bad at searching ] so asking where / who to buy from ?
Thanks
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I been reading though lots of threads on GPSDO, but still not figured out which to buy. Which of the versions of bg7tbl are most recommended and why?
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Same here... wondering which version (with display) is a good choice.
Mainly need it as reference for occational recalibration of my measurement equipment.
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It may seem like a stupid question but where can i find a full list of all terminal commands? Typing “help” doesn’t work. Also i ordered a proper gps antenna but what is the best diy antenna that i can use until i get the real one?
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Also i ordered a proper gps antenna but what is the best diy antenna that i can use until i get the real one?
I have just done an evaluation of a cheap active GPS antenna ($4AU) with a NEO-6 GPS module, the results were clear that the antenna is not critical, but where it is positioned is very important. In my opinion if there is enough signal strength to work, but the antenna position is poor, then upgrading the GPS module to a timing module will be more effective than getting a better antenna. I've attached my evaluation.
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Also i ordered a proper gps antenna but what is the best diy antenna that i can use until i get the real one?
I think the quadrifilar helix is a great DIY antenna.
https://www.eevblog.com/forum/beginners/suitable-gps-for-gpsdo-ocxo/msg1260063/#msg1260063 (https://www.eevblog.com/forum/beginners/suitable-gps-for-gpsdo-ocxo/msg1260063/#msg1260063)
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I was able to purchase a BG7TBL on Amazon and wanted to post pics of the internals here. It seems that this original design has matured to the point where the only real difference we're going to see is different OCXOs and possibly GPS modules.
The date on the board is 6-10-2021. Mine came equipped with a CTS Model 196 square wave output OCXO and uses an (unlabeled) Ublox NEO M8 GPS module. Well that's what Ublox U Center identified it as anyway.
The 1PPS signal is triggered on the rising edge and the 10 MHz sine wave is clean as far as I can see.
It is a NMEA receiver and Lady Heather has no issues communicating with it a straight through serial cable is all that's needed.
It draws a steady 400 mAh @ 12 volts as the OCXO warms up which drops to a steady 220 mAh afterward.
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The GPS receiver is pretty sensitive and I was able to achieve a steady GPS lock with the included puck antenna in the center of my basement lab. With the puck antenna in a basement window facing North (worst direction I know) with a partial view of the sky the SNR from LH over 24 hours was pretty bad. The majority of which was <20 SNR.
I quickly upgraded to an external antenna and from a bang for buck perspective ($35.00) I was very impressed with this Abracon AEACMK0660746-SG4 I purchased off Digikey.
Adapting it to a pole mount (since it mounts via a stud) took some doing but I was able to make it work (was able to find all of the hardware on Amazon). Mounted it about halfway up my roof. Used 25 feet of RG-58 as feed line with the antennas high LNA gain of 40 dB I wasn't too worried about loss over such a short run.
I'm pleased with the end result I consistently have a good signal from 10 satellites at all times.
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Looks like there is a new GPSDO, with supposedly rubidium disciplined oscillator. "GNSS-RB" on ebay.
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Wow. On aliexpress as well. In super sexy black no less.
It's out of my "just buy it and play" budget, so someone else will have to check it out.
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p.s love your content usagi, the Centurion (and up coming pdp) stuff has been fascinating. All the best to Sue. (p.s just joined as a new patron)
thanks, but i'm not usagi electric ;)
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Doh! Well, I'm sure you produce something, and all the best to "insert a person or pet in your life".. hahaha..
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Will be interesting to see pics of the inside of that - appearently it might be the same PCB as my GPSDO w/LCD (no dates on front/end of case), so wonder if it would be a 'simple' modification.
Main PCB says: GNSS-D-OCXO(RB) 2021-06-10
Display board says: 20210527
And LCD says: BG7TBL V20220808 when powering up.
I've already opted for a different gps disciplined rubidium standard, though.
Also; for the Trimble OCXO inside my unit - date code 1337, is that YYWW, ie. Week 37 Year 2013?
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Also; for the Trimble OCXO inside my unit - date code 1337, is that YYWW, ie. Week 37 Year 2013?
that would be my guess. lucky number 8)
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Hi @all,
I have a BG7TBL GPSDO with date from 2017-10-09.
After reading this thread here I also decided for better performance to change the CTS OCXO to a OSCILLOQUARTZ 8663-XS DOCXO and the GPS Module to a NEO-M8T from Mouser.
Regarding the infos I changed the resistor for the antenna voltage from 3.3 to 5 Volts and the multiplicator for the VC for the DOCXO to x2.
The Controlvoltage now is 4.7 Volts. I have to configure a little bit with U-Center to get all Sats (GPS, GLONASS and GALILEO) running. The stability is much better and I can use much more sats
to lock as before. Even a simple Puck antenna near my windows gets 22 Sats quickly.
On the downside of the circuit board the PPS led is blinking and Lady Heather is displaying a lot of data when I use the /rxu switch.
The one problem I see is that the BG7TBL device has its ALM and RUN leds permanently on. There will be a decreasing current after the DOCXO is stable:
(appr. 668 mA at the beginning to appr. 335 mA after nearly 2 minutes).
The pps output is running a normal pps signal and the 10 Mhz are also present.
The serial output at start is:
$GATXT,01,01,02,u-blox AG - www.u-blox.com (http://www.u-blox.com)*41
08:21:34 $GATXT,01,01,02,HW UBX-M8030 00080000*6F
08:21:34 $GATXT,01,01,02,EXT CORE 3.01 (111141)*36
08:21:34 $GATXT,01,01,02,ROM BASE 2.01 (75331)*16
08:21:34 $GATXT,01,01,02,FWVER=TIM 1.10*5F
08:21:34 $GATXT,01,01,02,PROTVER=22.00*17
08:21:34 $GATXT,01,01,02,MOD=NEO-M8T-0*72
08:21:34 $GATXT,01,01,02,FIS=0xEF4015 (100111)*57
08:21:34 $GATXT,01,01,02,GPS;GLO;GAL;BDS*78
08:21:34 $GATXT,01,01,02,SBAS;IMES;QZSS*46
08:21:34 $GATXT,01,01,02,GNSS OTP=GPS;GLO*38
08:21:34 $GATXT,01,01,02,LLC=FFFFFFFF-FFFFFFED-FFFFFFFF-FFFFFFAE-FFFFFF69*28
08:21:34 $GATXT,01,01,02,ANTSUPERV=*2D
08:21:34 $GATXT,01,01,02,ANTSTATUS=DONTKNOW*22
08:21:34 $GATXT,01,01,02,PF=3F2*30
Do I probably have to modify some further parameters in u-center to get the mcu working right?
There is as I see only UART1 active.
Thanks for helping.
Chris
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Update:
I have the suspicion that the 8663-XS may be no longer reach the 10 MHz because the Control Voltage was already high (4.7 Volts). This Voltage stays stable still after after 30 Minutes and longer running.
The ALM LED was on too. No switch to off after I exchanged the OCXO to the 8663.
I decided to change back the OCXO to the previous CTS OCXO and also the board mods as the supply voltage to 5 volts and the multiplicator back from x2 to x1 as well.
After Restart of the BG7TBL GPS OCXO the ALM Led and the RUN Led are on. With the old Ublox 7M the RUN Led was flashing after Start of the device.
Now after a few minutes the ALM Led switches off but no GPS Lock Led was going on as before. u-center sees more the 22 Satellites but no lock. The RUN Led is still permanently on.
Some ideas?
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Hi Chris,
I did something simimlar and changed to a ublox 8t and a morion ocxo.
Worked for me.
Regarding the leds:
The blinking stops as soon as you start LH in ublox mode -ru .
If you start LH in NEMA mode, the ledes will start to behave as before.
This did bug me for a while too, until I found out.
Regards
Chis
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Hi Chris,
thank you for this tip. I will try this out and hopefully all seems to be normal again.
Cheers Chris
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Hi Chris,
I did something simimlar and changed to a ublox 8t and a morion ocxo.
Worked for me.
Regarding the leds:
The blinking stops as soon as you start LH in ublox mode -ru .
If you start LH in NEMA mode, the ledes will start to behave as before.
This did bug me for a while too, until I found out.
Regards
Chis
Hi Chris,
unfortunately that does not help. On the pic you can see that my gps sat view is very good (active puc antenna on my window outside).
But the LOCK LED is still off and the RUN LED is permanently lighting.
Cheers Chris
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Hi Chris,
afaik, the 8663-XS needs 12V
https://www.miedema.dyndns.org/fmpics/Circuits_online/ocxo/8663_datasheet_ed.03-2003.pdf (https://www.miedema.dyndns.org/fmpics/Circuits_online/ocxo/8663_datasheet_ed.03-2003.pdf)
Please check. You can configure the board to supply 12V to the OCXO.
Regards
Chris
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Just wanted to add, finally getting the ublox NEO-M8T configured, enabled Galileo and tracking 20+ sats now. After a few other configuration changes I can say it seems to lock down to 0.00ppb very quickly and is rock solid. Still sorting through the 400 page book on this chip.
Hi kj7e,
did you have some configuration tips for my neo-m8t configuration? I can see all sats which I want (gps, galileo and glonass) but after exchange of the neo module my bg7tbl gpsdo will not run properly.
The RUN Led ist permanently on and the LOCK Led will no longer light on after the gpsdo is going in lock mode. It seems so because the frequency will be relatively stable after a few minutes but I cannot proof it.
Would be nice if you could help.
Cheers Chris
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There are many settings in the uBlox module to make it work as a stationary GPSDO (including setting the OCXO parameters and teach-in time for the stationary position). Having it locked doesn't say much as your clock output can still wander like crazy due to wrong settings. You need at least 2 other know-good GPSDOs to make a 3 cornered hat assesment of whether you modified GPSDO works OK. Every measurement needs to run for at least 24 hours, preferably 48 hours.
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Hi Chris,
afaik, the 8663-XS needs 12V
https://www.miedema.dyndns.org/fmpics/Circuits_online/ocxo/8663_datasheet_ed.03-2003.pdf (https://www.miedema.dyndns.org/fmpics/Circuits_online/ocxo/8663_datasheet_ed.03-2003.pdf)
Please check. You can configure the board to supply 12V to the OCXO.
Regards
Chris
Hi Chris,
yes I changed the SMD resistor to the 12 Volts place (see pictures in message #955) after exchange to the 8663 ocxo and back to the 5 volts place after changing back to the original ocxo.
Cheers Chris
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There are many settings in the uBlox module to make it work as a stationary GPSDO (including setting the OCXO parameters and teach-in time for the stationary position). Having it locked doesn't say much as your clock output can still wander like crazy due to wrong settings. You need at least 2 other know-good GPSDOs to make a 3 cornered hat assesment of whether you modified GPSDO works OK. Every measurement needs to run for at least 24 hours, preferably 48 hours.
Hi nctnico,
I have the suspicion that I forgot to configure the external ocxo source correct. So the pll is running infinitely without getting locked.
Cheers Chris
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Hi all,
I am looking for a NEO-M8T config file created with u-blox u-center 22.07 for comparing.
I was foolish not to save mine before I switched the NEO-7M receiver to an NEO-M8T :palm:
After desoldering the config has been gone (stored in the battery backed ram).
So now I can fiddle out which config I have to set for disciplinig the CTS ocxo (for minimizing more failure sources I put the builtin CTS ocxo back on the circuit board).
Cheers Chris
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Hi all,
I am looking for a NEO-M8T config file created with u-blox u-center 22.07 for comparing.
I was foolish not to save mine before I switched the NEO-7M receiver to an NEO-M8T :palm:
After desoldering the config has been gone (stored in the battery backed ram).
So now I can fiddle out which config I have to set for disciplinig the CTS ocxo (for minimizing more failure sources I put the builtin CTS ocxo back on the circuit board).
Cheers Chris
I configured a LEA-M8T a while back. I can't remember all the details (I should have written it down) but IIRC u-center 22.07 did not support the M8T (to set up the timing mode required a TIMER2 message, and for unknown reasons that isn't in 22.07). I found V8.29 online, and it worked fine.
There's a lot of things can be changed but I skipped most of it. Using u-center I reset the configuration, enabled some messages, restricted the satellite constellations to GPS and one other (I think Galileo) as recommended by others, ran the survey in for 24 hours, disabled the extra messages just leaving the normal NMEA messages, then saved the whole configuration to permanent memory (otherwise it gets lost on power down). It takes some reading of the u-blox8-M8_ReceiverDescrProtSpec_UBX-13003221-1.pdf document to understand the process, but it's all there.
I know I was confused by the survey in process, so I set it to survey in for a short period to learn about it. IIRC when it completes it doesn't say it has, but automatically goes into timing mode. But the details are a bit hazy now.
Good luck.
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I configured a LEA-M8T a while back. I can't remember all the details (I should have written it down) but IIRC u-center 22.07 did not support the M8T (to set up the timing mode required a TIMER2 message, and for unknown reasons that isn't in 22.07). I found V8.29 online, and it worked fine.
There's a lot of things can be changed but I skipped most of it. Using u-center I reset the configuration, enabled some messages, restricted the satellite constellations to GPS and one other (I think Galileo) as recommended by others, ran the survey in for 24 hours, disabled the extra messages just leaving the normal NMEA messages, then saved the whole configuration to permanent memory (otherwise it gets lost on power down). It takes some reading of the u-blox8-M8_ReceiverDescrProtSpec_UBX-13003221-1.pdf document to understand the process, but it's all there.
I know I was confused by the survey in process, so I set it to survey in for a short period to learn about it. IIRC when it completes it doesn't say it has, but automatically goes into timing mode. But the details are a bit hazy now.
Good luck.
Thank you for your tips. I found the u-center 8.29 on the u-blox download page for u-center. I give it a try. The over 400 pages of the M8 receiver description is hard stuff :phew:
Cheers Chris
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The over 400 pages of the M8 receiver description is hard stuff :phew:
Once you get the hang of u-center it isn't so hard. You don't need to know the format of every message, and that is over 300 pages. I played around modifying things without storing them in the permanent configuration, not knowing really what I was doing (but learning). A reboot cleared any mistakes and start again. I think 22.07 prompts to say do you want to store this, but 8.29 doesn't and you have to remember in the end that data has to be stored in the permanent config to become permanent. I've seen a few comments "I did this but when I rebooted it went back to how it was".
Hang in there.
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The display versions of the BG7TBL GPSDO can display an indication of the accuracy of the 10MHz signal.
It is not clear to me, how the unit determins this
Maybe a calculated result of TDOP?
Is there a way to get this info from a non-display BG7TBL GPSDO, for example via LadayHeather?
Regards
Chris
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I have two of the 2021-06-10 GPSDO boards upgraded to UCT 108663-01's, was curious if anyone knows how to use the crystal vref to drive EFC? I can confirm swapping R4/R5 for 5V/12V and the X1/X2/X3 information from older boards is still valid but botched my attempt to validate swapping C53 to C44 for the upgrade from a CTS 196 to UCT 108663-01, as such I didn't attempt it on my second unit (currently using a bodge wire from the new to old crystal RF output post)
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Hi, general question for the group. I have a BG7BTL with date code of 2019-10-20, PCB date code is 2021-06-10. This unit has a Trimble 72344 ocxo, would anyone have the specs on this ocxo. Mainly interested in the EFC pin control specs.. Trying to see if it might be possible to remove this reference and use the Efratom FRS-C rubidium in its place. The FRS-C has a control pin 0 - 5V. If anyone can point me in the right direction that would be much appreciated. Picture attach of the reference.
There is a PCB on eBay that seems to be already setup for rubidium but no info on EFC output. Here is a picture of that board. Picture 7001 is the back of the rubidium PCB.
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Could you please share the right configuration for M8T? Of if you have a link where is already explained I would thank you. Cheers.
Got one of these in a bid and I have m8T module.
By thr way my M8T has the time pin exposed, would be enough use that pin without need solder /desolder the chip?
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Hi,
just a question : what's the short term stability of this populated PCB ?
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I was able to purchase a BG7TBL on Amazon and wanted to post pics of the internals here. It seems that this original design has matured to the point where the only real difference we're going to see is different OCXOs and possibly GPS modules.
I know that you posted on this a year ago, but I wonder if you know anything about that connector on the PCB, labeled LCD? It would be nice to add an LCD display to this.
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Will be interesting to see pics of the inside of that - appearently it might be the same PCB as my GPSDO w/LCD (no dates on front/end of case), so wonder if it would be a 'simple' modification.
Main PCB says: GNSS-D-OCXO(RB) 2021-06-10
Display board says: 20210527
And LCD says: BG7TBL V20220808 when powering up.
I've already opted for a different gps disciplined rubidium standard, though.
Also; for the Trimble OCXO inside my unit - date code 1337, is that YYWW, ie. Week 37 Year 2013?
That LCD pinout looks like a standard 16x2. The connector to the main board only has 6 pins. You'd need 2 for power/gnd and 4 for data. Are the control lines hard wired? Would you try to figure out how that display board is wired? I just ordered a GPSDO without display.
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That LCD pinout looks like a standard 16x2. The connector to the main board only has 6 pins. You'd need 2 for power/gnd and 4 for data. Are the control lines hard wired? Would you try to figure out how that display board is wired? I just ordered a GPSDO without display.
My guess:
Most likely, the the dislpay board has a separate microcontroller, which receives serial data from the ublox chip via the 6-pin connector. The data is then processed for the display controller. 'I very much doubt, that you can directly connect a standard display.
I too have a unit without the display and if there is an easy way to retrofit a display, I would be interested.
On the other hand, you could use a raspberry pi with a dispay running Lady Heather ...
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It may just use an I2C adapter, too.
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The GPSDO I ordered from Amazon just arrived. The PCB is marked 2021-06-10, and looks exactly like the pics posted earlier. The same CTS OCXO and unmarked GPS. Yes, I took it apart before turning it on.
Now that I have a better look at the PCB, I can see that the LCD connector is actually labled "ISP-LCD". It is indeed connected to the SPI pins on the nearby ATmega 328p. So, in addition to programming the 328p, the uC is controlling the optional LCD via four digital I/O's (the other two pins are Vcc and Gnd).
Upon power up, it takes less than a minute to get a fix. The serial port uses a straight-through cable, at 9600, n, 8, 1.
u-center identifies the GPS as an M8030, 32 channels, with firmware 3.01 in ROM. I can't tell if there is any flash without trying to upgrade the firmware or taking the lid off the GPS (not going to happen). I believe v3.01 is the last version firmware, so there is no need to look for flash. I doubt that uBlox is going to release a newer firmware for M8 chips at this point. So, it's not a real uBlox GPS, but uses a uBlox M8030 chip. I don't think this is the Timing version GPS. The v3.01 firmware supports all of the current GNNS systems.
Looking at the config in u-center, only GPS is enabled (good for a GPSDO). NAV5 is set to Stationary, Auto 2D/3D. SBAS is set to Disabled. TP (timepulse) has a cable delay of 820 ns (I'll have to see if this corresponds to the length of the coax on the included antenna). TMODE is Disabled (probably best to set this to Survey-in for hours, once placed in its permanent location). The other settings look to be standard defaults.
Next, I tried Lady Heather. LH auto identified the GPSDO as standard NMEA. LH had a squashed display, but pressing F11 made it go full screen. The picture was taken after about half an hour since power on for the second time (first time was with u-center). I've never used LH before, so I'll have to read the docs to see what the graph means, and why it dings at me occasionally.
So far, so good. Next, I'll hook it up to my 11-digit frequency counter and see how it tracks with my HP 58540A GPSDO that has been running for about 2.5 years, since I moved.
Edit: I forgot to mention that the GPS is spitting out only NMEA sentences, no ubx. Of course, this can be changed in u-center.
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I should add the pinout of the 6-pin connector. There is no pin 1 mark, so I'll call pin 1 the top pin, when the 328p is to the left. The third column is the pin number on the 328p.
1 - Gnd
2 - MISO - 16
3 - SCK - 17
4 - /RESET - 29
5 - MOSI - 15
6 - Vcc
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I unplugged the power for a few minutes, to move it upstairs and hook things up to compare with my HP 58540A GPSDO. It has a battery, so I assume it didn't have to do a cold start (which didn't take long the first time). I don't know if any OCXO tuning parameters are stored or not.
Looks good so far. The alarm LED went out in just a few minutes. In less than ten minutes, it was within a few milliHertz of my HP 58540A GPSDO. I'll log the data for 24 hours and post a graph, later.
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I measured the length of the coax on the included antenna. The coax is unlabeled, but looks like RG174. Calculating the delay gives 18.7 ns. I don't know why the GPS module is programmed with a huge 820 ns delay. Does anone have a clue?
After reading the Lady Heather manual, it looks like it can measure all the delays. After I'm finished collecting data for the comparison to my HP GPSDO, I'll hook up LH and see what I get.
I'll probably also start LH in ubx mode, instead of the default NMEA mode. This is supposed to give me more info.
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I found the manual and just read it. It has a block diagram but no detailed information. I see that the PPS from the GPS goes to the CPLD. So, the question is, does the CPLD read from the u-blox GPS and do sawtooth correction before passing it on to the 328p and the BNC?
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I measured the length of the coax on the included antenna. The coax is unlabeled, but looks like RG174. Calculating the delay gives 18.7 ns. I don't know why the GPS module is programmed with a huge 820 ns delay. Does anone have a clue?
After reading the Lady Heather manual, it looks like it can measure all the delays. After I'm finished collecting data for the comparison to my HP GPSDO, I'll hook up LH and see what I get.
I'll probably also start LH in ubx mode, instead of the default NMEA mode. This is supposed to give me more info.
It has been reported, that the BG7TBL has an offset of around 2mHz for the 10MHz output. It is mot clear, if this is true for all versions of the BG7TBL.
I have verfied this on my unit against a Samsung GPSDO with a TinyPFA phase frequeny analyzer.
For most application, this is probably a non-issue.
It is my understanding, that the cable delay is used to compensate the phase delay of the 1 pps output. It does not influence the accuracy of the 10MHz output oft the GPSDO.
And yes, running LH in ubx mode gives more info.
Chris
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After 12 hours, I'm getting from 0-3 mHz low on this model. I had read about the offset on earlier models, but was under the impression that it was fixed on recent models (I don't remember the year).
I'm still curious as to why mine came with such a huge delay. This is certainly not a default.
I also have a NanoVNA H4. It was my intention to flash the PFA firmware on it and test again, with that. I've not used Timelab. Are there any recommended settings for this type of measurement?
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After 12 hours, I'm getting from 0-3 mHz low on this model. I had read about the offset on earlier models, but was under the impression that it was fixed on recent models (I don't remember the year).
I'm still curious as to why mine came with such a huge delay. This is certainly not a default.
I also have a NanoVNA H4. It was my intention to flash the PFA firmware on it and test again, with that. I've not used Timelab. Are there any recommended settings for this type of measurement?
I too did the conversion of a NanoVNA-4H to TinyPFA by reflashing it.
Getting it to work with Timelab was straigt forward, even for a Timalab noob like me.
I have the settings on another pc. If you have problems, I can check.
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Some results, after logging data for 24 hours. I was using my HP 11 digit counter (showing me single mHz) with it's external reference hooked to my HP 58540A GPSDO, which has been running continuously for about 2.5 years. Both GPSDO's were on the same HP timing antenna via a splitter (I plan on getting an amplified antenna splitter, but the passive one seemed to work fine). Data was collected using a Prolific GPIB-USB dongle and EZGPIB, setting the counter to a 10 second gate time. I have not done a survey-in yet.
If I make a graph with all 24 hours of data, it will be too huge, and still won't show the fine data. So, I'll summarize. At 140 seconds, it stabilized at +/- 0-4 mHz. At that point the Alarm LED went out. It stayed +/-0-4 mHz for several hours. Later, it stayed +/-0-3 mHz for several more hours. During the last several hours it settled on 10000000.000 and 9999999.999 (mostly 10000000.000). That LSD may just be due to my counter.
Looking at the data, it is interesting that the frequency is low much more often that it is high. I assume that has something to do with the firmware and how it tunes the OCXO.
Here is a small graph, showing the initial warm up. It gets within 4 mHz of 10 MHz quickly. However, this was not a total cold start, as earlier I had it running while I looked at the GPS module with u-center. It was then unplugged for 10-15 minutes.
I conclude that this revision hardware/firmware does not have the frequency offset reported for earlier revisions (at least to the mHz resolution).
Next, after I finish setting up a spare mini-PC, I'll run Lady heather on this GPSDO, using /rxu to force u-blox binary mode. I understand that this will make a difference in what is reported to the software vs the default NMEA mode that is autodetected. I'll also do a survery-in for a day or two with LH. I'm new to LH, so I'm not sure what I'll see.
Later, I plan on flashing my NanoVNA H4 with the PFA firmware. I have no idea how much better data I'll get with a PFA vs my HP counter. I hope I can get a few more digits, to see how this GPSDO really performs.
As mentioned above, my counter only lets me see to single mHz. If I did the math right, 1 mHz from 10 MHz is 1E-10. Good enough for anything I need, but a good GPSDO should be 100 times better than that.
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I got LH running. I had some trouble with the built-in Comm 1 port, so for now I'm using a USB-serial adapter. After a second read through of the docs, I set a bunch of command line options (Edit: I forced ubx mode). I can't find how to turn off the satellite displays. I'd like to have the graph wider.
For some reason, I can't get any of the video resolution options to give me a full screen display. I'm using a 1080p TV via HDMI, but F11 and /vh crashes, /vf and /vc=1920x1080 gives me a smaller screen, and everything I tried has fonts too small to read. The best so far is the default of 1024x768.
After fooling around a bit, I turned on SBAS (GPS was already on) and started a 48 hour survey with SP. Shortly after, I did a screen capture.
I understand what most of the text means. Are the satellite signal levels (dBc) good? I'm going through a passive splitter with my HP timing antenna. I understand what the graph in the upper right is. I'm not so sure what the graph at the bottom is showing me. I did turn on ADEV.
If I understand things, after the survey is done, I can turn off SBAS, then do an EE to write the surveyed position back to the u-blox GPS. Then I may want to increase the elevation mask and save that.
Any words of wisdom or enlightenment about any of this is appreciated.
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Before starting LH, I fired up my HP 8920B to see what the 10 MHz sinewave looked like. The level measured about 12 dBm. The second harmonic was at -35 dBm (-47 dBc) and the other harmonics were in the noise. For harmonics, I set the span from 0-100 MHz.
I understand that the OCXO puts out a squarewave, so the LPF is doing an excellent job.
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Hi, I won a bid if this GPSDO with no display, CTS oscillator and original labeled Neo7 , I don't remember if 7n or 7m , but I can open again of needed.
It gets lock quite fast in indoor with my antenna that is triband and 3-V.
I made and db9 cable with TX to RX to a ftdi and displayed in ucenter , 8.1 old version used in Neo7 years and the last one 23.xx I think. With both U-center versions can see the sats it locks, 10 average in the room, and precision is absolutely enough with that, I wont put outside the antenna.
The problem is that even reading the sats, it doesn't read the config, firmware version, or anything and I can change nothing, all the gnss tab boxes appears detached, the firmware empty...any idea of why this behaviour?
Maybe my cable is wrong and I should buy a commercial one?
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I understand what most of the text means. Are the satellite signal levels (dBc) good? I'm going through a passive splitter with my HP timing antenna. I understand what the graph in the upper right is. I'm not so sure what the graph at the bottom is showing me. I did turn on ADEV.
If I understand things, after the survey is done, I can turn off SBAS, then do an EE to write the surveyed position back to the u-blox GPS. Then I may want to increase the elevation mask and save that.
Any words of wisdom or enlightenment about any of this is appreciated.
In my experience, signal levels over 35 dB are good. If there are reflected signals it can cause a problem, the elevation mask can help there. Only if your antenna is in a poor position. If you get a survey in less than a metre then it's not a worry.
I think, but someone will know better, that when survey in completes the GPS module writes the data to memory itself and enters timing mode automatically. I did it a year or two ago and that might be my faulty memory.
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In my experience, signal levels over 35 dB are good. If there are reflected signals it can cause a problem, the elevation mask can help there. Only if your antenna is in a poor position. If you get a survey in less than a metre then it's not a worry.
I think, but someone will know better, that when survey in completes the GPS module writes the data to memory itself and enters timing mode automatically. I did it a year or two ago and that might be my faulty memory.
Yes, that would be if I had the GPS do a self survey. I opted to let LH do a survey, as it says it will be more precise.
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The problem is that even reading the sats, it doesn't read the config, firmware version, or anything and I can change nothing, all the gnss tab boxes appears detached, the firmware empty...any idea of why this behaviour?
Maybe my cable is wrong and I should buy a commercial one?
That's weird. Perhaps it is your cable. You're obviously receiving data. Maybe you aren't transmitting to the GPS. When you use u-center, it sends commands to put the GPS in ubx mode.
My GPSDO is configured to NMEA mode on power up (I assume all the different revisions are). u-center should be receiving the NMEA data, which is why you're seeing satellites.
The cable needs to be straignt through. I initially used a cable made with ribbon cable and IDC connectors.
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Looking at the LH display (below), the GPS module is obviously reporting sawtooth corrections (the numbers change every second). Is there any way to tell if the GPSDO itself is using this to actually make the corrections to the PPS?
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I did the cable myself with a connector and two cables to the ftdi, can be seen in the picture. Maybe I need ground too.
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I'd say that's a definite yes.
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Something wrong, I connected PIN5 (gpsdo's GND I guess, as it's the GND pin of RS232) to the GND im the FTDI adapter and will stop even of receiving.
I bought a RS232 to USB , but I think what I have should work
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After letting LH run its precision survey for 48 hours, I used u-center to enter those fixed coordinates into the GPS receiver. I also turned off SBAS and set the elevation mask to 15 degrees. To make sure that the changes stuck, I power cycled the GPSDO and checked again.
After powering the GPSDO again, the LOCK LED came on in seconds. It took right at two minutes for the ALARM LED to go out. This time, I turned on ADEV in LH. I let it run overnight.
After running about nine hours since the last power up, I get the ADEV numbers shown in the picture. LH says this about ADEV:
"Heather calculates ADEVs based upon the PPS and OSCillator error values reported by the unit. These values are not derived from measurements made against an independent reference (other than the GPS signal) and may not agree with ADEVs calculated by measurements against an external reference signal."
So, what are these numbers really telling me about the performance of this GPSDO? Is it really that good? If a more accurate source is not the comparison reference, what can I infer about these numbers?
I also see that LH reports that the sawtooth accuracy has improved by 20 ns. From this, I gather that LH itself is making sawtooth corrections?
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Related to the last post, I see that the two plots (which I think are showing me oscillator tuning and PPS tuning?) are much less jumpy than before the survey. Is this due to the survey, or the fact that the oscillator is simply settling in after a few days (not counting a brief power down)?
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Related to the last post, I see that the two plots (which I think are showing me oscillator tuning and PPS tuning?) are much less jumpy than before the survey. Is this due to the survey, or the fact that the oscillator is simply settling in after a few days (not counting a brief power down)?
I have no experience with Lady Heather, so no idea what the graphs tell you. The PPS improves after survey in, as it can now calculate corrections for ionospheric conditions etc. But it will still have a sawtooth component, due to the clock in the GPS module not being synced to anything. You will also get an improvement as an oscillator beds down, usually a slow drift in one direction which gets smaller as days go by. It is good practice to not move the GPSDO once it is running. Brief power down will have some short term effect, mainly due to the temperature of the oven dropping then going back up. Moving it can disturb the mounts, and that is a small but long lasting effect. I inverted my GPSDO once to see what effect it had, changed the control voltage by quite a bit.
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Thanks for the reply. I understand that the PPS is better after the survey, as that was the reason for doing it. I also know that it takes a while for an oscillator to settle. I'm hoping that someone who knows the intricacies of LH will respond, and enlighten us all.