[time-nuts] A question about anomolous Alan Deviation Measurements.

morrie at iometric.com morrie at iometric.com
Sun Sep 21 22:55:46 EDT 2014

I am using a Fluke PM6690 counter measure the Alan Deviation
of various pairs of 10 MHz OCXO's in use in my lab.

I discovered that I can measure a (tau = 1 sec) low value of say 6.0E-12
on a good set, but only If the crystals are tweaked so the delta is some
0.5 ppm.  If they crystals are tweaked to be within a mH, then the Alan
Deviation zooms to about 5 times higher.

I suspect a flaw in my PM5590 unit or in its design, and I guess will
hunt around for something better.

Does anyone have experience with this phenomena?  Does one always
have  to separate the clocks being compared to avoid this "beating"?

Morrie Altmejd

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