The heart of any crystal radio is the Germanium Diode. Modern silicon diodes require too much power to operate, so they are useless in the extremely low power circuitry of a crystal radio. Germanium Diodes are not as available as they used to be and good, sensitive ones are a little difficult to find. We test each one of our Germanium Diodes in a crystal radio circuit to verify its performance. Diodes may be the IN34A or IN270 variety. Either type will work just as well as the other. Package of 1 diode. Limited quantities available.