[time-nuts] oscillators

Magnus Danielson magnus at rubidium.dyndns.org
Thu Aug 30 21:23:09 UTC 2012

On 08/30/2012 11:10 PM, Rick Karlquist wrote:
> Azelio Boriani wrote:
>> Interesting this third overtone/fundamental*3 idea but what makes the
>> third
>> overtone not equal to the fundamental*3? Is the crystal operated in series
>> or parallel resonance?
> That is where the special SC cut crystal comes into play.
> It's not so much that the 3rd OT is on a different frequency, but
> rather that it has a different and known tempco relative to the
> fundamental, so it can be used as a thermometer.  It would be
> interesting to take a crystal out of a random 10811 and compare the
> frequencies of the fundamental and 3rd OT vs temperature to see
> if that crystal would accidentally make a good thermometer.

All the different modes have different temperature dependencies. Being 
able to maintain dual oscillation on both over the range seems like a 
reasonable challenge.


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