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-boun...@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. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
