bg7tbl gpsdo master reference

[Jörg]

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*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*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

[Jörg]

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

[DaJMasta]

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.

[TSL]

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

[DaJMasta]

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.

[ted572]

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

[Jörg]

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

[VK4GHZ]

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

[ted572]

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.   

[kj7e]

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.

[cdev]

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.

[Jörg]

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
.

[TheUnnamedNewbie]

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....

[Jörg]

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.

[ted572]

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).  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

[Jörg]

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

[Jörg]

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).  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.

[kj7e]

Jorg, which antenna are you using now?  How does it differ from the one supplied?

[Jörg]

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.

[kj7e]

Found a PCTEL GPS L1 antenna for cheap on eBay;
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.

[Jörg]

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,

[gr8tfly]

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

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.)

[ted572]

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.      Cheers, Ted

[gr8tfly]

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!

[ted572]

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