FM modulation is most simply done with a voltage controlled oscillator, i.e one where the frequency is dependant on a voltage. A Varactor diode changes its capacitance depending on the voltage across it, so if that diode is used as a capacitor in an oscillator circuit, then the frequency will deviate depending on voltage, so can be used as a FM modulator.OK, I think I understand that, how far the carrier frequency deviates back and forth within its bandwidth determines loudness and how frequently it is deviating is the pitch. It's a little hard to visualize. I don't really understand exactly how the musical signal modulates the carrier frequency or vice versa, but I don't guess I need to know lol.
S