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

Ralph Devoe rgdevoe at gmail.com
Tue Feb 13 13:46:03 EST 2018

Hi Tom,

to reply to your questions:

(1) Yes, I was also surprized at how good the 5065a is. It's a stock unit
that has apparently never been repaired or modified. I'm guessing it was
turned off for a long time (the seller said it was stored in an unheated
container in Alaska).  Leo's lab is very quiet, it's in a subbasement of a
new building with good  temperature control. The 5065a was installed there
in November and had run a month before the tests. Before that it was on for
> 6 months  in my shop.

(2)  The simultaneous test would be much better, but we were worried that
digital noise from the fitter would leak back through the power splitter
into the 53230a and provide noise. The ADC chip in the fitter is connected
directly to the input line using a wideband Minicircuits transformer, and
might be noisy. An isolation amplifier would fix this. Still this is a good
suggestion and  we should try this out.

The fitter is running continuously and we have about a dozen 200K second
runs stored. I have one of Corby's barometric chips and a data logger, so
we trying to correlate the temperature and pressure with the results.


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