[time-nuts] Improving the stability of crystal oscillators

Rick Karlquist richard at karlquist.com
Thu Oct 11 14:52:15 EDT 2007

At HP, in the 90's, we did a lot of brainstorming about vacuum ovens.
This never seemed to make sense to us.  If you actually
achieve high amounts of thermal resistance, then you can't
get the heat out of the oven.  And if you don't, why bother
with a vacuum.  Also, a vacuum only helps if you do everything
else you need to do to make a true Dewar (thermos bottle), like
having mirrored surfaces, etc.  Finally, having a vacuum means
that nothing that outgasses can be used in the oscillator.
Maybe Vectron has figured out something we didn't think of or
has sufficiently difference constraints that a vacuum makes
sense for them.

Rick Karlquist N6RK

SAIDJACK at aol.com wrote:

> Today there are some interesting new technologies which allow small
> double,
> or even tripple (not sure if that makes sense) ovens to be built. Vectron
> for
> example just had a lead-article in RFDesign magazine  introducing their
> newest evacuated OCXO's.
>    _http://rfdesign.com/vlf_to_uhf/time_and_frequency/709RFDF1.pdf_
> (http://rfdesign.com/vlf_to_uhf/time_and_frequency/709RFDF1.pdf)
> They claim stabilities on the order of 2E-07 over a very wide temp  range
> of
> -40 to +85C in a DIP14 can.
> The 1/2 size DIP8 can is supposed to be available end of the year with
> similar performance.
> Those small cans and wide operating ranges should make it possible to
> build
> a nice small and inexpensive oven. If one can get a true thermal gain of
> 1000+, then that would theoretically mean stabilities approaching 2E-010
> over
> temperature. That's 1.6E-012 per degree Celcius.
> bye,
> Said

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