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

[Michael Wouters]

We have operated  about 40 PRS10s over the past 20 years or so. These are
all run continuously in benign environments and monitored via GPS
time-transfer . Some have died after just over a year; others have operated
for more than 12 years. A new one generally takes a few months to burn in,
before its frequency drift stabilises to something like the specifications.
They do not behave very predictably, showing sudden changes in frequency
and so on. One exhibited frequent steps for a few years and then the
problem went away. Trying to predict what they would do at the level of
better than a few parts in 10^11 seems difficult.

 Cheers
Michael


On Sat, 9 Mar 2019 at 3:03 am, Attila Kinali <attila at kinali.ch> wrote:

> 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
> --
> It is upon moral qualities that a society is ultimately founded. All
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>                  -- Miss Matheson, The Diamond Age, Neal Stephenson
>
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