[time-nuts] Orbiting crystals

Tom Van Baak tvb at LeapSecond.com
Sat Jun 27 11:07:22 EDT 2009


Hi Antonio,

A couple of thoughts...

First, remember the quartz crystals on the GPS SV are not
free-running; they are just the LO of Rb or Cs atomic clocks.

So you can partly answer the question yourself with a simple
experiment at home. Have you ever seen frequency jumps in
any of your cheap Rb or Cs clocks at home? Even one? If so
how big was the jump?

Second, can you better define what you mean by "frequency
jump"? This is a familiar but vague term. In some respects one
can say that every crystal, that every oscillator has frequency
jumps.

The frequency averaged over one tau is always different than
than the frequency over the next tau, and the next, etc. If not,
the ADEV would be zero. But as you know ADEV is never
zero. The purpose of clock statistics is to show how close to
zero it is. So it would be good for you to define your threshold
of "jump" before we talk too much more about detecting them.

/tvb





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