Magnetic Resonance Amplifier 3: Capacitor Instead Of Piezo Element

Please watch the first two videos first.
Here I take the Piezo element out of the circuit and replace it with a capacitor of similar value.

The circuit behaves nearly the same as before (only quieter). The capacitance of the Piezo I am using is 35-40 nF, and I replaced it with 50 nF ceramic capacitor. Since the capacitance is now a bit larger, the resonant frequency has also changed. I read it as around 72-73 kHz based on the scope traces and the Philips counter reading.

And this is just what the theoretical calculation gives. The coil primary measures about 99 microHenry on the ProsKit meter, so with 50 nF capacitance in a series resonant tank we obtain about 71.5 kHz from the standard formula.

With the 37 nF piezo element we obtain about 83 kHz from the formula, just as we measured in the last video.

My favorite resonant frequency calculator:
http://www.1728.org/resfreq.htm

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