On 8/29/12 8:45 PM, Richard (Rick) Karlquist wrote:
On 8/27/2012 11:45 PM, WB6BNQ wrote:
A microprocessor controlled XO is a non oven crystal oscillator system
that has
additional computational control providing a bit more than just mere
passive
temperature compensation. The additional computational capability
deals with
having coefficients of that particular oscillator's behavior pre coded to
compensate for the nonlinear behavior over a given temperature rang
It doesn't use coefficients. It has a look up table of frequency vs
temperature.
A microprocessor controlled XO system allows for using cheap crystals
with
minimum processing time and costs. Because of limited storage space
there is no
No it doesn't use a cheap crystal. It uses a *special* SC cut crystal.
This crystal could very easily cost more than an OCXO crystal.
Isn't the crystal cut (and the circuit designed) in such a way that it
supports both the fundamental and the third overtone simultaneously, and
comparing the frequencies of the two (or, more accurately, fF- fthird/3)
is how they measure the temperature, which is then used to look up the
correction factor in a PROM.
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