AVR-Chat

Just a "temperature compensated crystal" won't do it. At
that 
level, the oscillator, itself has a major effect. Instead,
a 
TCXO (Temperature Compensated Xtal Oscillator) is needed.
This is an entire oscillator plus crytal in a "box" and
compensated,
often digitally.

Jim


On Sat, 12 Aug 2006 16:40:37 -0400
 "David VanHorn" <microbrix@gmail.com> wrote:
> > i am looking for a precise SMT crystal that has
> temperature
> > compensation feature ... anyone have seen such product
> in the internet?
> > i had searched dozens of crystal manufacturers but i
> didnt see one.
> > i dont know if such product really exist.
> > most crystals available have -0.03 to -0.04
> PPM/C^2(degree celcius
> > squared) at -40C to 85C temperature range.
> 
> 
> Precision oscillator design is somewhat of an art.
> You'll need more than just a stable crystal.
> Getting the crystal isn't that hard, just email Statek,
> or one of the
> others, and tell them your requirements. They can do
> customs.
> 
> The rest of the circuit will need to be designed though..
> The caps and
> resistors selected to match the crystal, and the rest.
> 
> For example, I have a couple of repeaters that use
> crystals to determine
> transmit and receive frequency. They do NOT use any
> ovens, the whole thing
> draws less than 30mA on standby  :)    But the oscillator
> circuits have
> seven thermistors, and are quite complicated.
> 5ppm -40C to +60C is guaranteed. It's the sort of thing
> that you typically
> helicopter to the peak of a mountain and leave for a few
> years.
> 
> 
> [Non-text portions of this message have been removed]
> 

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