[time-nuts] Am I doing something wrong?

[Bob kb8tq]

Hi

If your OCXO tunes to 10 MHz at -3.5V and it used to tune at +0.5V, it sounds like the tune line is shorted somewhere. 
That could be inside the OCXO or outside. If the short is “noisy”  (and that is not unusual) you aren’t going to get it to lock.
You need to figure out where the short is. Best guess would be inside the OCXO.

Bob

> On Sep 26, 2019, at 11:06 AM, Roger Rehr W3SZ <w3sz at comcast.net> 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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