[time-nuts] Oscillators and Ovens

Chris Caudle chris at chriscaudle.org
Wed Nov 1 16:58:44 EDT 2017

On Wed, November 1, 2017 3:38 pm, Hal Murray wrote:
>> In general, OCXOs have crystals with high Q -> low phase noise,
>> especially
>> compared to a TCXO, which *can't* have high Q, or the  temperature
>> compensation circuit can't do it's work.
> I don't understand that.  Why can't I build a high Q TCXO?

Compensation implies pulling the frequency away from the natural
resonance.  High Q implies that the frequency cannot be pulled very far
away from natural resonance.
The two items are directly contradictory.

Chris Caudle

 I don't need
> to
> change the compensation very fast.  Are good crystals high enough Q that
> it
> would take too long?
> What's the time constant?  I'd guess it's Q/freq, maybe with factors of
> 2pi
> or e or ???
> That seems small relative to how fast temperature changes.  (but maybe
> fast
> relative to FCC smearing or things like that)
> --
> These are my opinions.  I hate spam.
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