The diode in a 'crystal' radio is the basic demodulator of AM transmissions. Note that the front-end RF can be amplified and the back-end audio can be amplified to give a very usable AM radio.
As a kid, I had a one-transistor audio amplifier that was inserted between the crystal set and the headphones. It made a huge difference.
As a kid, I had a one-transistor audio amplifier that was inserted between the crystal set and the headphones. It made a huge difference.