[time-nuts] Crystal jumps and unjumps

[Hal Murray]

I'm seeing jumps in the frequency from a crystal, and a while later, jumps 
back to the previous frequency.  (or as close to it as I can measure)

I get roughly 1 a month.   The jump is about 0.2 PPB.

The crystal is inside an HP 5234B with option 010, the high stability oven 
oscillator.

Has anybody seen anything like this before?
Is there a term for it?
What should I look for?  ...

Graphs and such for 4 examples:
  https://www.glypnod.com/TimeNuts/jump/jump.html

18 hours, 2 hours, 1/2 hour, and 10 minutes.





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