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Crystal radio receiver

The Crystal radio receiver was first built c1900 by Greenleaf Whittier Pickard[?], who used crystalline minerals to detect radio signals. A crystal rock was fixed inside a brass cup and the radio operator found the loudest signal by touching the wire, called a cat's whisker, to various points on the surface of the crystal.

People first built and used simple and inexpensive crystal radio sets without batteries or electrical power. Even though vacuum-tube radios were common following World War I, crystal radios remained popular, especially among beginning amateur radio enthusiasts, Boy Scouts and school children, who built crystal radios to learn basic electronics and communication.

During the Great Depression parents would build a crystal radio detector from inexpensive galena crystal and a safety pin[?]. After this detector was connected to iron bedsprings (which doubled as an antenna) and grounded to household cold-water pipes, a youngster needed only inexpensive headphones. GIs during World War II constructed similar radios from rusty razor blades and pencil lead, the iron oxide crystals of the rust replacing the galena crystal and the graphite of the pencil lead substituting for the safety-pin wire. These crude, but functional, radios were nicknamed foxhole radios.

One hundred years after their first use, hobbiest still build and tinker with -- and listen to -- crystal radios constructed from just a few parts.

Components

Diode, coil, earphone, antenna ground

Schematic

[Image]

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