bg7tbl gpsdo master reference

[usagi]

Thread to collect all the bg7tbl information into a single reference.

A chinese ham "bg7tbl" 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"
custom board with surplus russian morion mv89 OCXO. gps is u-blox. both sine and square wave output variants available.

"2014-12-09"
custom board with surplus russian morion mv89 OCXO. gps is u-blox NEO-6M-0-001.

"2015-07-08"
custom board with surplus oscilloquartz star 4 (oscilloquartz "STAR 4") gpsdo board. OCXO is oscilloquartz 8663-XS. gps is u-blox LEA-5T-0-002.

"2015-07-17"
custom board with surplus trimble "57963-D" gpsdo board. OCXO is trimble 73090. gps is unknown.

"2015-09-17"
custom board with surplus russian morion mv201 OCXO. gps is u-blox NEO-6M-0-001

"2015-09-17" (variant 1 - mv89a)
custom board with surplus russian morion mv89a OCXO. gps is u-blox NEO-6M-0-001

"2015-09-17" (variant 2 - bliley nvg47a1282 )
custom board with surplus bliley nvg47a1282 OCXO. gps is u-blox NEO-6M-0-001

"2016-05-31"
custom board with surplus bliley nvg47a1282 OCXO. gps is u-blox NEO-7M-0-000
AVR dump available in this post.

"2017-03-29"
custom board with surplus cts 970-2178 OCXO. gps is u-blox NEO-7M-0-000

"2017-09-23"
custom board with unknown OCXO. gps is unknown. compact design.

"2017-10-09"
custom board with surplus cts 970-2178 OCXO. gps is u-blox NEO-7M-0-000

"2017-12-16"
custom board with unknown OCXO. gps is unknown. backlit LCD display.

"2019-09-23"
custom board with surplus bliley nvg47a1282 OCXO. gps is unknown. compact design.

"2017-10-20"
custom board with unknown OCXO. gps is unknown. backlit LCD display.

"GNSS-RB"
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. 

[usagi]

"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. 

http://www.ke5fx.com/gpscomp.htm

[usagi]

"2014-12-09"

review by tim tuck / VK2XAX

[usagi]

"2015-07-08"

surplus oscilloquartz gpsdo.
uses oscilloquartz star 4 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.

[usagi]

"2015-07-17"

surplus trimble gpsdo.
appears to use same "uccm board" as the 2015-07-17 (oscilloquartz) model.

[Lightages]

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.

[edpalmer42]

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

[motocoder]

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.

[edpalmer42]

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

[usagi]

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 if you want one to experiment on.

[motocoder]

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 if you want one to experiment on.

Link doesn't work.

[Vgkid]

I would be interested to see the performance of the Huawei Oscilloquartz model. It potentially has the best specced ocxo.

[usagi]

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 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

[TSL]

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.

[Selectech]

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.

[Fraser]

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

[dadler]

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!

[motocoder]

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.

[usagi]

other than excellent sensitivity, the huawei/oscilloquartz star4 speaks both NMEA and UBLX. and the UBLX is very a well documented protocol.

[motocoder]

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.

[usagi]

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.

[usagi]

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.

[motocoder]

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?

[usagi]

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.

[motocoder]

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 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

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.