[time-nuts] Am I doing something wrong?

[Roger Rehr W3SZ]

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