A
crystal radio receiver, also called a
crystal set or
cat's whisker receiver, is a very simple
radio receiver, popular in the early days of radio. It needs no other power source but that received solely from the power of
radio waves received by a wire
antenna. It gets its name from its most important component, known as a
crystal detector, originally made from a piece of crystalline mineral such as
galena. This component is now called a
diode.