[time-nuts] Am I doing something wrong?

[Bill Beam]

It looks like since last Oct the osc jumped frequency and has become less stable.
This is not unheard of for an ocxo.  It may be time to replace with a true
Trimble Thunderbolt.  A couple are now on ebay for 2-300$.  It is possible to
replace the ocxo, assuming nothing else is wrong with the circuit.

On Thu, 26 Sep 2019 13:21:25 -0400, Roger Rehr W3SZ wrote:

>Hi All,

>Sorry I forgot to attach the freq vs DAC voltage table to the email that 
>I just sent:
>DAC V-  Freq
>+5.0- - - -  9.999.961
>+0.0- - - -  9.999.985
>-3.0- - - -  9.999.998
>-3.5- - - -  10.000.000
>-3.8- - - -  10.000.001
>-4.0- - - -  10.000.002
>-4.5- - - -  10.000.004
>-5.0- - - -  10.000.006

>So the oscillator is not "centered" on 10.000.000 anymore.

>73,
>Roger
>W3SZ

>On 9/26/2019 1:06 PM, Roger Rehr W3SZ wrote:
>> Hi Nigel, and Bob, and Bill!
>>
>> Thanks for the notes!-  I very much appreciate your helpful comments.-  
>> I will give my responses to all of your helpful posts here.-  Sorry for 
>> the delay in responses.-  The reason for the delay is that my 
>> Thunderbolt is at a remote site and I can communicate with it via Lady 
>> Heather remotely, but I had to drive out to the site to do the tests 
>> with an HP 5342A frequency counter and pulse analysis of the pps 
>> port.-  I drove out to the site today.
>>
>> First, Bob and Bill,
>>
>> 1.
>> DAC set to +0.5 V gives significant frequency errors:-  HP counter 
>> reads 9.999.984 MHz and osc error as reported by LH is 1,68x,xxx.xx 
>> ppt.-  Interestingly, at this voltage pps error is flipping between +50 
>> and -50.
>>
>> The DAC voltage that minimizes both counter error and pps/osc error as 
>> reported by LH is around -3.553 V.-  This is dramatically different 
>> than the setting last October when all was working well, as you know.
>>
>> With DAC voltage -3.553 V the osc error and pps error are reduced, but 
>> they jump around quite a bit:
>> pps short-term variation is for example between about +50 and -50 and 
>> osc short term variation is between about +5000 and -5000.-  HP counter 
>> reads 10.000.000 MHz.
>>
>> Even when I have the DAC close enough to optimum that my counter reads 
>> 10.000.000 MHz and the osc error is flipping around both sides of 
>> zero, the unit stays in "Power-up" mode and the DAC voltage stays at 
>> wherever I set it (either using d>>s or &>>i and then power cycle) and 
>> does not vary.
>>
>>
>> 2.
>> I get a 10 usec duration +5V pulse every 1.00 seconds from the PPS 
>> port, as per specifications.-  I cannot give you greater precision than 
>> that on the pulse interval.
>>
>>
>> Nigel,
>>
>> I agree that something appears odd with this unit that had been 
>> running with no problems for at least a year at my location.-  There 
>> have been no known system / config changes by me, although there is 
>> always the chance that I fat-fingered something when playing with the 
>> Lady Heather display at some point.
>>
>> The receiver self identifies as a TSIP (Trimble TSIP Binary) receiver 
>> when Lady Heather starts up.-  The receiver type is not specified in my 
>> cfg file, which instead has the default line /rx which as you know 
>> means auto-detect receiver type.
>>
>> I had assumed that the "Nortel NTGS/NTBW" designation that you mention 
>> and that appears on the Lady Heather parameter display had something 
>> to do with Trimble having supplied the unit I now have to Nortel and 
>> this "Nortel NTGS/NTBW" designation being a custom ID placed in the 
>> firmware so that the unit would be "branded" as Nortel.-  This 
>> supposition is consistent with line 2170 of the heather.txt file which 
>> says "Trimble telecom GPSDOs (NTBW,NTPX,NTGS,etc)".-  There is also a 
>> line in the heather.pdf file that says, "Note that non-Thunderbolt 
>> GPSDOs (such as the NTBW and NTPx telecom devices) do not all support 
>> saving disciplining parameters to EEPROM and some do not allow users 
>> to change the disciplining parameters. You can use "/d" command line 
>> options for setting the PLL parameters from the command line. If you 
>> run the auto-tune command on non-Thunderbolt devices then only the 
>> satellite elevation mask (and perhaps the signal level mask) values 
>> will be set".
>>
>> The physical unit is labeled "Trimble THUNDERBOLT", so I guess, 
>> looking at all of the data, that I have a Trimble / Nortel device.
>>
>> But the issue of whether it is a Nortel/Trimble Thunderbolt or just a 
>> Thunderbolt wouldn't cause the current problem that I am having now in 
>> a unit that previously worked perfectly for me.
>>
>> Just so you know that my heather.cfg file is "OK" and not responsible 
>> for any problems, here it is:
>>
>> /9
>> /rx
>> /br=9600:8:n:1
>> /ro=1*
>> /tz=-5EST/EDT
>> /b=1
>> /tb=W3SZ
>> /gm
>> /gw=0
>> /gqw
>> /gcs-
>> /gcg
>>
>> To further document that this issue is not a "setup" problem, I did 
>> another factory reset of the unit and then did not use Lady Heather 
>> but only monitored function with TBoltMon.exe and I did not do any 
>> setup with that utility until the self survey was done and more than 
>> two hours had passed, and then I only set and saved the position. 
>> Function and-  results were unchanged, and the unit was still stuck in 
>> Power-Up mode and DAC voltage was still stuck at zero, but everything 
>> else was normal according to the TBoltMon readouts.
>>
>> Thanks again and 73,
>>
>> Roger
>> W3SZ
>>


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Bill Beam
NL7F