[time-nuts] OCXO settling
Paul A. Cianciolo
paulc at snet.net
Wed Sep 14 21:34:48 UTC 2011
>> When an OCXO is unpowered for some time, it undergoes a further ageing
process when it starts up next. This is specified in some data sheets, and
can typically require an hour of burn-in for each day left unpowered before
specifications are met.
This is one thing I was curious about. I am asking these questions because
I am working with a Rakon/C-MaC double oven OCXO.
As I make changes to the power supply, cabinet, EFC power supply,
surrounding this OCXO, I wondered how long to let the unit run before I run
a standard test on it using TimeLab.
Maybe 2 days would be a good compromise?
Paul A. Cianciolo
"Time is relative" Abert Einstien circa 1950
"Relatives use up all my time" Lisa Cianciolo circa 1983
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Murray Greenman
Sent: Wednesday, September 14, 2011 3:29 PM
To: time-nuts at febo.com
Subject: [time-nuts] OCXO settling
There are of course many levels of performance in OCXOs, but in general the
ageing slows down with time, and veteran OCXOs can be very good. I recently
tested the OCXO in an old HP5245L counter (circa 1970), last calibrated in
1985, and it was still within 100ppb of 10MHz after 24 hours warmup!
One point other correspondents didn't answer is the isue of retrace. When an
OCXO is unpowered for some time, it undergoes a further ageing process when
it starts up next. This is specified in some data sheets, and can typically
require an hour of burn-in for each day left unpowered before specifications
To answer the question about whether it is best to leave an OCXO turned off
when not in use (so it doesn't 'wear out'), I'd suggest that if you don't
plan to use it again for a month, turn it off - otherwise leave it running
all the time. It should get better with time.
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