[alfsch]

(14.03.2025, 10:32 AM)Gucki schrieb: And the frequency changes significantly:




Of course, this still needs to be checked for faults. It is conceivable that the piezo reacts to the changed stray capacitance.

The piezo may have to be placed in a shielded housing. And then series of measurements must be made. 

Wolfgang

So you checked the tuning by stray capacitance now - fine !

Better:
Just use a standard crystal, maybe 1 MHz, in a metal can HC-18 (-> grounded !) , then try again. 



-- and screen connecting wires also !!!
ANY changing stray capacitance will change frequency - thats the standard way, to tune crystal oscillators.