crystal radios
Galena-based audio devices
A crystal radio is a simple receiver that picks up AM radio signals without batteries or external power, drawing energy from the radio waves themselves.
The "crystal" refers to a mineral detector (originally galena) that converts radio signals to audio.
Crystal radios were popular in the early 20th century and remain common educational projects: We built crystal radios in science class.
- cat's whiskerThin wire detector probe
- signalsConveyed indications
- earphonePersonal audio receiver
- tuningAdjusting pitch accuracy
- diodeOne-way semiconductor
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