[time-nuts] Are there SC-crystals out there in the wild that are not Overtone?

[Bernd Neubig]

Basically you are right. One of the problem is, that SC-cut crystals possess
a strong "B-mode" resonance just 9% above the desired stable "C-mode". The
B-mode has a similar or even a bit lower resistance than the C-mode, and has
a temperature coefficient of -30 ppm/K. It is a temperature sensing mode,
and sometimes used for that purpose.
The existence of two close modes with similar resistance makes SC-cut
oscillator design a bit of an art, but not magic.

Bernd

-----Ursprüngliche Nachricht-----
Von: time-nuts [mailto:time-nuts-bounces at lists.febo.com] Im Auftrag von
Bruce Griffiths
Gesendet: Freitag, 28. Februar 2020 12:08

The idea is to see what frequency the crystal oscillates at not to build a
high stability oscillator.
If can be made to oscillate at a frequency somewhere around 5MHz/3 then its
likely a third overtone crystal.