How a Crystal Radio Works

Full details of how a crystal radio works, right down to the electron level. We start with a demonstration of all the parts in action, showing how the radio waves interact with the antenna and antenna coil to produce a fluctuating magnetic field, which induces electron flow in the tuning coil, which works with the tuning capacitor, which is followed by the diode and crystal earpiece. We talk about why a leaky germanium diode is needed with this particular circuit or how a bypass resistor can be used instead. That’s followed by how the tuning is done using a tuning coil in parallel with a tuning capacitor, which together are tuned to a resonant frequency the same as the radio frequency by adjusting the coil’s inductance and the capacitor’s capacitance. Then we show how a radio wave is formed from a microphone’s audio wave using amplitude modulation (AM). This then shows how the diode is necessary for converting the radio wave back to an audio wave for use by the earpiece or