[time-nuts] How far can I push a crystal?

Rick Karlquist richard at karlquist.com
Fri Jan 18 04:50:47 UTC 2013


Bernd Neubig wrote:

> A parallel inductor for compensation of the static capacitance C0 does not
> help much at 10 MHz, because such a coil, which resonates out a 6 pF
> capacitance has an internal winding capacitance, which is larger than 6
> pF.
> So you would need a coil which has a self-resonance of slightly above 10
> MHz.

Actually, a parallel inductor helps a lot and is essential for getting
a large pulling range.  Modern surface mount coils have a self capacitance
of a fraction of a pF, not 6 pF, and in any event, you can always find
an inductor that is resonant when combined with the crystal.  The
nominal value of this inductor may be considerably less than the
calculated value, but there is always some value of inductor that works.
This was true even in the through hole era.

Rick Karlquist N6RK




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