[time-nuts] Z3805 incident

[Charles P. Steinmetz]

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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