Radio Receiver Design - Crystal Radio

Crystal Radio

A crystal radio uses no active parts: it is powered only by the radio signal itself, whose detected power feeds headphones in order to be audible at all. In order to achieve even a minimal sensitivity, a crystal radio is limited to low frequencies using a large antenna (usually a long wire). It relies on detection using some sort of semiconductor diode such as the original cat's-whisker diode discovered long before the development of modern semiconductors.

• Advantages
  • Simple, easy-to-make. Here we see a classic design for a clandestine receiver in a POW camp.
• Disadvantages
  • Insensitive, it needs a strong RF signal and/or a long-wire antenna to operate.
  • Poor selectivity since it only has one tuned circuit.