[time-nuts] Weird GPSDO behavior - update
tshoppa at gmail.com
Wed Oct 4 10:45:46 UTC 2017
Is there a way you can force your currently disciplined oscillator to
free-run, and log the phase difference between oscillator and GPS over a
couple of days?
On Tue, Oct 3, 2017 at 2:15 PM, Skip Withrow <skip.withrow at gmail.com> wrote:
> Hello Time-Nuts,
> Well, I think I know a little more about my GPSDO problem, but
> probably have more questions now than before. Thanks for all the
> replies to the first post with thoughts and suggestions.
> I first tried restarting Lady Heather and doing a cold boot on the
> NTGS50AA (then entering the same disciplining values). Same behavior.
> I let it run over the weekend and the same behavior happened on
> Saturday and Sunday morning.
> So, yesterday (Monday morning) I changed the gain to the gain of the
> oscillator (.0072Hz/V), damping to 1.2, and time constant to 900s. On
> the attached PRS10-2 plot you can see that it quickly settled. This
> morning, it looks like all is well from the plot (about an hour before
> the furnace kicks in at the right of the plot). HOWEVER, when the
> plot is expanded there is still funny business going on with the DAC
> control voltage at the same time of day. I just think the changed
> parameters limit the disturbance. The expanded plot is the attached
> At this point I'm beginning to think that the NTGS50AA is the issue,
> but there are lots of questions left.
> 1. There are various version of the NTBW50AA/NTGS50AA GPS/operating
> firmware. Mine is 10.3 and I notice that it has the LH 'ro'
> designation (as does the 10.4 version). The 10.5 version does not
> give the LH ro notice. Maybe it behaves better with the disciplining?
> I will have to give a 10.5 a try.
> 2. Why does the glitch occur at 8am in the morning? Will have to try
> powering the NTGS50AA up at different times and see it the glitch
> moves around.
> 3. Which disciplining parameters are affected by this glitch and which are
> 4. Have other people seen this same behavior? Does it happen on
> Thunderbolts too?
> I'll update again when I have more data.
> Skip Withrow
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