On 4/22/16 12:41 PM, Hal Murray wrote:
jim...@earthlink.net said:
But what about when the observations have gaps? Say you're measuring the
frequency of a spacecraft oscillator, and you can only see it for 8 hours a
day?
One interesting question... Can you match up the cycles after the gap? Is
your clock stable enough or do you have a slower clock (PPS?) that you can
lock on to.
probably can't match the cycles..
It's a sort of generalized question, but say your clock is a OCXO with
1ppb sort of accuracy, that's 1E-9 in a long term sense, and after
20,000 seconds of a 10 MHz clock, you'll have accumulated 200E9 cycles.
If your frequency changed the 1ppb, that's 200 cycles error.
And I think that gets to my underlying question, is such a measurement
meaningful? What statistic, other than, say, "frequency error measured
at 24 hour intervals, with 1000 seconds of counting for each
measurement", which is sort of like ADEV with tau of 86400, but not really.
And would that really help with understanding of hte underlying
mechanisms. For oscillators, knowing that there's a difference between
1/f^3 and 1/f and 1/1 phase noise and then seeing the output of an
oscillator helps you to optimize the overall system design. if the white
noise floor is really high, then improving flicker noise may not help.
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