[time-nuts] 10811 Extra Lagging etc

Richard (Rick) Karlquist richard at karlquist.com
Wed Jun 21 01:17:50 EDT 2006

The crystal is definitely hermetic.  I am pretty
sure it is not thermal and is not related to the
oven.  It is not even the transistor because it
is also hermetic (not so much by design but more
an accident of it being a legacy design).  The
#1 suspect would be the piston trimmer that adjusts
the frequency.  Early on in the development of
the 10811, they had a bad problem with aging that
turned out to be lubricant in the piston trimmer.
They switched to unlubricated trimmers.  The varactor
diode might also be a possible source of drift.

Rick Karlquist N6RK

> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
> Behalf Of Hal Murray
> Sent: Tuesday, June 20, 2006 7:45 PM
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] 10811 Extra Lagging etc
> > Yes, I did, because nobody else had, and I was curious. We were seeing
> > changes along the lines of parts in 10^8, about an order of magnitude
> > worse than tempco.  This was for something like dry nitrogen purge all
> > night vs 50 degrees C, 90% humidity for an hour or two.
> Does anybody understand the mechanism?
> I assume the actual crystal itself is sealed.  I'd guess that
> something in
> the control electronics in humidity sensitive.  Do FR4 boards change size
> with humidity?
> Is the thermal conductivity of humid air enough different from dry air to
> change the internal temperature of various parts?
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