[time-nuts] Question on disciplining oscillators

SAIDJACK at aol.com SAIDJACK at aol.com
Tue May 2 18:40:28 EDT 2006

Hello Javier,
this depends on your Rb oscillator, and if you use an external DAC  circuitry 
then the DAC and DAC reference thermal sensitivity as well.
Typically, the Rb including the DAC and DAC reference will be  better than 
the GPS for time frames from 1000 to 10000s. The GPS  will probably be better 
than the Rb above 10000s and should thus be  allowed to correct the Rb at such 
longer intervalls.
So try starting with a cut off frequency of around 3000s, then try 10K or  
even 20K intervalls for really good Rb's. Keep in mind that your DAC and DAC  
reference likely have 2-5ppm temperature coefficient themselves, and may thus  
affect your Rb accuracy.
Simple OCXO's seem to work well with a time constant of around 1000s or  less 
since they are much worse than the GPS at those times and benefit from the  
GPS corrections above 1000s measurement intervalls.

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