Usually metal detectors work with the difference of a reference oscillator and the tank circuit with the air coil. I was wondering if this maybe works aswell. So first I have a collpits tuned at around 500kHz with the 10uH being the air coil. This is then fed in a pulse counting frequency demodulator and then through a LPF to creat a average voltage according to the frequency of the LC tank. This is then fed into a VCO which is tuned to audible frequencies. Now the VCO's cap is a 1000 times smaller than it would be just to compensate for sampling rate. I guess the low pass will have to be adjusted accordingly. And I think the sim is having some issues with the PCFDM. Pls let me know what you think of that.
