[time-nuts] Aging rate of crystals

Rick Karlquist richard at karlquist.com
Tue Feb 19 23:27:00 UTC 2008


Mike Fahmie wrote:
> Somewhere, I have a NASA pub that describes a technique using Gamma Rays
> to
> accelerate aging so that later aging is much reduced, can't seem to find
> it
> now. I would guess that the radiation cause the stresses to relax. NASA
> was
> evidently interested because satellites experience a lot more radiation
> than we receive here on the surface and it probably caused a rapid
> frequency shift in otherwise unradiated crystals.

I remember some of the crystal gurus talking about this.
I suspect it didn't pan out or everyone would be doing it.
I also remember them saying that radiation causes "color centers"
to appear.

> I have two HP quartz oscillators that I've been running and logging for
> well over a decade. They run 24/7 and are on battery backup. The HP-103
> shows about 6 parts in 10^-12/day and the HP-107 about 2 parts in
> 10^-13/day. I attribute this to steady temperature and solid mounting in a
> heavy rack.
>
> -Mike-

That's incredible Mike.  I've never seen a 10811 or E1938 within a
factor of 10 of the first number you gave, let alone the second.
The second rate would be very respectible for a Rb standard.
I believe those antique oscillators you have are using non-HP
made xtals at 1 MHz (or 5 MHz at the most) in glass packages.
While a steady temperature and solid mounting is great, it takes
more than that to put up these kind of numbers.  Congratulations, keep
taking good care of those old war horses.  I wish Len Cutler were
still around to tell about it.  He proudly keep a 107 prototype
in his office.  Len couldn't bring himself to design anything that wasn't
a doomsday machine.

Rick Karlquist, N6RK





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