[time-nuts] Allan variance by sine-wave fitting

Tom Van Baak tvb at LeapSecond.com
Mon Feb 12 17:30:48 EST 2018

Hi Ralph,

Nice test. Two comments.

1) Your 5065A is working really well; is it one of Corby's "super" ones? What sort of environmental controls did you have during the run, if any. How long had the 5065A been powered up before you ran the test?

2) Is there a reason you didn't or couldn't make simultaneous measurements using both counters? That would have allowed an interesting study of the residuals. Plots of phase, frequency, spectrum, and ADEV of the residuals provides insight into how well the two counters match. This would also probably remove the awkward divergence of your two ADEV plots past tau 1 hour.


----- Original Message ----- 
From: "Ralph Devoe" <rgdevoe at gmail.com>
To: <time-nuts at febo.com>
Sent: Monday, February 12, 2018 1:52 PM
Subject: [time-nuts] Allan variance by sine-wave fitting

> I've been comparing the ADEV produced by the sine-wave fitter (discussed
> last November) with that of a counter-based system. See the enclosed plot.
> We ran the test in Leo Hollberg's lab at Stanford, using a 5071a Cesium
> standard and my own 5065a Rubidium standard. Leo first measured the ADEV
> using a Keysight 53230a counter with a 100 second gate time. We then
> substituted the fitter for the counter and took 10,000 points at 20 second
> intervals. The two systems produce the same ADEV all the way down to the
> 5x10(-14) level where (presumably) temperature and pressure variations make
> the Rb wobble around a bit.
> The revised paper has been published online at Rev. Sci. Instr.

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