Author Topic: bg7tbl gpsdo master reference  (Read 243908 times)

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Offline ted572

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Re: bg7tbl gpsdo master reference
« Reply #575 on: March 05, 2018, 12:52:17 pm »
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
« Last Edit: March 06, 2018, 02:42:48 pm by ted572 »
 

Offline istamov

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Re: bg7tbl gpsdo master reference
« Reply #576 on: March 06, 2018, 05:35:45 pm »
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)?
 

Offline ted572

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Re: bg7tbl gpsdo master reference
« Reply #577 on: March 06, 2018, 06:54:38 pm »
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
 

Offline istamov

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Re: bg7tbl gpsdo master reference
« Reply #578 on: March 06, 2018, 08:21:52 pm »
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?
 

Offline ted572

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Re: bg7tbl gpsdo master reference
« Reply #579 on: March 06, 2018, 09:08:02 pm »
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.
« Last Edit: March 06, 2018, 09:24:14 pm by ted572 »
 

Offline texaspyro

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Re: bg7tbl gpsdo master reference
« Reply #580 on: March 06, 2018, 10:33:03 pm »
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".
 

Offline ted572

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Re: bg7tbl gpsdo master reference
« Reply #581 on: March 07, 2018, 03:06:17 am »
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  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.
« Last Edit: March 08, 2018, 08:30:19 pm by ted572 »
 
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Offline ted572

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Re: bg7tbl gpsdo master reference
« Reply #582 on: March 08, 2018, 04:26:10 pm »
"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/, 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, 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.
« Last Edit: March 08, 2018, 10:22:32 pm by ted572 »
 
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Offline kj7e

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Re: bg7tbl gpsdo master reference
« Reply #583 on: March 11, 2018, 11:15:33 pm »
This video just popped up, in Polish, but shows startup to stabilization.

 
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Offline ted572

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Re: bg7tbl gpsdo master reference
« Reply #584 on: March 13, 2018, 06:18:17 pm »
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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Offline Jörg

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Re: bg7tbl gpsdo master reference
« Reply #585 on: March 13, 2018, 09:05:15 pm »
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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Offline Jörg

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Re: bg7tbl gpsdo master reference
« Reply #586 on: March 13, 2018, 09:09:55 pm »
In case of second best, it looks like this:
« Last Edit: March 13, 2018, 09:11:27 pm by Jörg »
 

Offline Jörg

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Re: bg7tbl gpsdo master reference
« Reply #587 on: March 13, 2018, 09:19:04 pm »
In the so far worst case it looks like this:
 

Offline rfspezi

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Re: bg7tbl gpsdo master reference
« Reply #588 on: March 28, 2018, 01:18:32 pm »
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.
 

Offline metrologist

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Re: bg7tbl gpsdo master reference
« Reply #589 on: March 28, 2018, 03:31:19 pm »
I think what comes up also is jitter specification.
 

Offline texaspyro

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Re: bg7tbl gpsdo master reference
« Reply #590 on: March 28, 2018, 03:50:15 pm »
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.
 

Offline kj7e

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Re: bg7tbl gpsdo master reference
« Reply #591 on: March 28, 2018, 04:01:50 pm »
KE5FX did measure the phase noise of a 2015 version BG7TBLGPSDO;
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.
 

Offline lty1993

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Re: bg7tbl gpsdo master reference
« Reply #592 on: April 08, 2018, 06:36:17 am »
Got mine yesterday. It is dated 2017-12-16 on the front. Clock TIE measured by MSOS804A.
« Last Edit: April 08, 2018, 06:40:13 am by lty1993 »
 
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Offline Jörg

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Re: bg7tbl gpsdo master reference
« Reply #593 on: April 08, 2018, 03:56:33 pm »
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,
« Last Edit: April 08, 2018, 08:39:43 pm by Jörg »
 
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Offline Jörg

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Re: bg7tbl gpsdo master reference
« Reply #594 on: April 08, 2018, 05:15:27 pm »
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.
« Last Edit: April 08, 2018, 05:17:06 pm by Jörg »
 
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Offline Jörg

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Re: bg7tbl gpsdo master reference
« Reply #595 on: April 13, 2018, 01:29:31 pm »
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.
« Last Edit: April 13, 2018, 02:02:27 pm by Jörg »
 

Offline Jörg

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Re: bg7tbl gpsdo master reference
« Reply #596 on: April 13, 2018, 01:40:56 pm »
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.
 

Offline Jörg

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Re: bg7tbl gpsdo master reference
« Reply #597 on: April 13, 2018, 01:47:15 pm »
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.
« Last Edit: April 13, 2018, 01:56:51 pm by Jörg »
 

Offline kj7e

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Re: bg7tbl gpsdo master reference
« Reply #598 on: April 13, 2018, 02:49:48 pm »
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.
« Last Edit: April 13, 2018, 03:33:24 pm by kj7e »
 

Offline Jörg

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Re: bg7tbl gpsdo master reference
« Reply #599 on: April 13, 2018, 05:39:59 pm »
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.
« Last Edit: April 13, 2018, 06:42:08 pm by Jörg »
 


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