[time-nuts] PRS-10 Warm-up Time, Calibrating/Adjusting, and long-term poweron

[Attila Kinali]

On Fri, 8 Mar 2019 06:31:48 -0600
Dana Whitlow <k8yumdoober at gmail.com> wrote:

> The point here is that there are apparently a number of warm up drift
> mechanisms operating, some of which take days to sensibly settle down.

Longer. I know of one measurement, where the Rb had a kind of stable
drift until it suddenly switched to another slope quite suddenly
(within a few days) about half a year after power up.

The aging mechanisms of Rb vapor cell standards are many and not
all of them are well understood, much less controlled. Compared
to that, an OCXO has "only" thermal stability of the oven, strain
relaxation of the holder/crystal and deposition/removal of contaminants
on the crystal surface. Ok, there are a couple more, but these three
are the main contributors for most OCXO out there. While for the
Rb vapor cell standard I could name you half a dozen just like that
and I am far from being an expert on these.

For those interested, John Vig wrote a couple of papers on the aging
of OCXO in the 80s and 90s. The topic of Rb vapor cell aging is a lot
more messy and I don't know whether there is any good paper that reviews
the main contributors.

			Attila Kinali
-- 
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