[time-nuts] Z3805 incident
Charles P. Steinmetz
charles_steinmetz at lavabit.com
Thu Nov 29 07:32:37 UTC 2012
Volker wrote:
>>When looking at the PPS TI vs. time curve today I felt kind of
>>appalled - a big incident peak (not an outlier) on the curve! See picture.
>>
>>What happened to my Z3805? Any idea?
Said responded:
>This is a classic crystal jump. The crystal changed its frequency
>magically from one second to the next and the software compensated for it
Here is another example of a 3805 having a bad moment. For just
about two minutes, it reported a phase jump of nearly 3 uS and then
immediately fell back nearly to its previous baseline, settling to
the baseline in about an hour and not requiring any longer-term
change of the EFC voltage. This does not look like a typical crystal
frequency shift to me, but I cannot rule that out. It looks more
like what I'd expect to see if I set the cable delay to 3 uS for 2
minutes, then back to 0.
The 3805 shares an antenna with two Thunderbolts, neither of which
showed any anomaly at that time. It had been running stably for
weeks, and has been running stably since the anomaly (it has not been
running long enough that the drift rate has reached a stable value --
it is still coming down).
Thank you, Ulrich, for the Z38XX monitoring program!
Best regards,
Charles
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