[time-nuts] Improving the stability of crystal oscillators
SAIDJACK at aol.com
SAIDJACK at aol.com
Thu Oct 11 13:43:55 EDT 2007
In a message dated 10/11/2007 09:12:44 Pacific Daylight Time,
richard at karlquist.com writes:
>Your last statement is not generally true. The block cannot be well
>insulated because of the thermal overhead of the oven circuitry (the
>heat has to escape). I explained in my 1997 FCS paper how to achieve
>the isothermal condition, which is achieved by symmetry rather than
>high amounts of insulation. The E1938A oven works quite well if the
>insulation is omitted or replaced by poor insulation, except that it
>consumes more power.
>Rick Karlquist N6RK
Hi Rick,
thanks for the pointers to the E1938A oven quality.
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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