Author Topic: bg7tbl gpsdo master reference  (Read 186626 times)

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Offline Vgkid

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Re: bg7tbl gpsdo master reference
« Reply #25 on: August 18, 2015, 09:38:15 pm »
I emailed him, and never got a response back.
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Offline motocoder

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Re: bg7tbl gpsdo master reference
« Reply #26 on: August 18, 2015, 10:31:30 pm »
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.
 

Offline motocoder

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Re: bg7tbl gpsdo master reference
« Reply #27 on: August 19, 2015, 04:23:35 pm »
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 ?
 

Offline edpalmer42

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Re: bg7tbl gpsdo master reference
« Reply #28 on: August 19, 2015, 06:55:51 pm »
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
 

Offline Vgkid

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Re: bg7tbl gpsdo master reference
« Reply #29 on: August 19, 2015, 07:58:47 pm »
Just for the 5t, try hooking up two wires to the usb pin( the 6 has one).
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Offline Lightages

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Re: bg7tbl gpsdo master reference
« Reply #30 on: August 19, 2015, 09:44:59 pm »
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/

Any thoughts?
 

Offline edpalmer42

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Re: bg7tbl gpsdo master reference
« Reply #31 on: August 19, 2015, 10:10:00 pm »
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/

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
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

Ed

 

Offline motocoder

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Re: bg7tbl gpsdo master reference
« Reply #32 on: August 19, 2015, 10:34:12 pm »
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?
 

Offline motocoder

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Re: bg7tbl gpsdo master reference
« Reply #33 on: August 19, 2015, 10:35:16 pm »
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.
 

Offline usagi

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Re: bg7tbl gpsdo master reference
« Reply #34 on: August 20, 2015, 10:25:00 am »
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).

Offline edpalmer42

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Re: bg7tbl gpsdo master reference
« Reply #35 on: August 20, 2015, 05:30:30 pm »
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
 

Offline Lightages

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Re: bg7tbl gpsdo master reference
« Reply #36 on: August 21, 2015, 12:21:08 am »
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.
 

Offline TSL

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Re: bg7tbl gpsdo master reference
« Reply #37 on: August 21, 2015, 12:54:56 am »
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

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

VK2XAX :: QF56if :: BMARC :: WIA :: AMSATVK
 

Offline Vgkid

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Re: bg7tbl gpsdo master reference
« Reply #38 on: August 21, 2015, 01:44:30 am »
Hopefullly they will stay in stock until Christmas. Currently e-mailling oscilloquartz about the star 4 module.
If you own any North Hills Electronics gear, message me. L&N Fan
 

Offline Lightages

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Re: bg7tbl gpsdo master reference
« Reply #39 on: August 21, 2015, 06:20:04 am »
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

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.
« Last Edit: August 21, 2015, 06:25:11 am by Lightages »
 

Offline TSL

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Re: bg7tbl gpsdo master reference
« Reply #40 on: August 21, 2015, 06:44:27 am »
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

under the heading "Using a Serial - USB converter"

regards

Tim
VK2XAX :: QF56if :: BMARC :: WIA :: AMSATVK
 

Offline Lightages

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Re: bg7tbl gpsdo master reference
« Reply #41 on: August 21, 2015, 06:51:32 am »
Thanks again. Like I said I wasn't sure how to do it yet. There is lots to wade through on that web site.
 

Offline Lightages

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Re: bg7tbl gpsdo master reference
« Reply #42 on: August 21, 2015, 09:14:40 pm »
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.
 

Offline motocoder

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Re: bg7tbl gpsdo master reference
« Reply #43 on: August 21, 2015, 09:34:10 pm »
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).


 

Offline Lightages

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Re: bg7tbl gpsdo master reference
« Reply #44 on: August 21, 2015, 09:41:37 pm »
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
 

Offline TSL

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Re: bg7tbl gpsdo master reference
« Reply #45 on: August 21, 2015, 10:58:08 pm »
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
VK2XAX :: QF56if :: BMARC :: WIA :: AMSATVK
 

Offline Lightages

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Re: bg7tbl gpsdo master reference
« Reply #46 on: August 21, 2015, 11:24:13 pm »
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.
 

Offline motocoder

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Re: bg7tbl gpsdo master reference
« Reply #47 on: August 21, 2015, 11:41:46 pm »
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
« Last Edit: August 22, 2015, 12:19:05 am by motocoder »
 

Offline motocoder

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Re: bg7tbl gpsdo master reference
« Reply #48 on: August 21, 2015, 11:43:06 pm »
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.
 

Offline Lightages

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Re: bg7tbl gpsdo master reference
« Reply #49 on: August 22, 2015, 12:02:56 am »
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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