Author Topic: bg7tbl gpsdo master reference  (Read 187594 times)

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Offline n3mmr

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Re: bg7tbl gpsdo master reference
« Reply #775 on: September 18, 2019, 09:25:05 am »
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?
 

Offline kj7e

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Re: bg7tbl gpsdo master reference
« Reply #776 on: September 22, 2019, 01:24:09 am »
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.
 

Offline kj7e

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Re: bg7tbl gpsdo master reference
« Reply #777 on: September 22, 2019, 01:34:58 am »
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
« Last Edit: September 22, 2019, 02:05:55 am by kj7e »
 
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Offline haydenph

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Re: bg7tbl gpsdo master reference
« Reply #778 on: October 09, 2019, 10:05:13 pm »
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?


 

Offline akumiszcza

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Re: bg7tbl gpsdo master reference
« Reply #779 on: October 22, 2019, 07:30:12 am »
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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Offline akumiszcza

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Re: bg7tbl gpsdo master reference
« Reply #780 on: October 22, 2019, 09:10:44 am »
Photos of the inside. Board date is 2019-01-07.
 
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Offline akumiszcza

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Re: bg7tbl gpsdo master reference
« Reply #781 on: October 22, 2019, 10:15:17 am »
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).
 

Offline texaspyro

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Re: bg7tbl gpsdo master reference
« Reply #782 on: October 22, 2019, 06:22:03 pm »
-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.
 

Offline akumiszcza

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Re: bg7tbl gpsdo master reference
« Reply #783 on: Yesterday at 05:58:05 am »
-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).
 

Online jonese

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Re: bg7tbl gpsdo master reference
« Reply #784 on: Today at 12:19:27 am »
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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