[time-nuts] Improving the stability of crystal oscillators

[SAIDJACK at aol.com]

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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