Crystal radio – 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 battery or power source and runs on the power received from radio waves by a long wire antenna. It gets its name from its most important component, known as a crystal detector, originally made with a piece of crystalline mineral such as galena. This component is now called a diode.
Crystal radios are the simplest type of radio receiver and can be handmade with a few inexpensive parts, like an antenna wire, tuning coil of copper wire, capacitor, crystal detector and earphones. They are passive receivers without amplifier. The rather weak sound must be listened to with sensitive earphones, and can only pick up stations within a limited range.
Crystal radios get their power from the radio signal themselves. There’s no need to supply batteries or plug into a wall socket.
The diagram shows a common crystal radio circuit, used in inexpensive crystal radios sold today. The tuning coil L1 and capacitor C1 together make up the tuned circuit; it selects the radio signal to be received, out of all the signals picked up by the antenna. C1 is adjustable, and is used to tune in different stations. The crystal detector D1 rectifies the radio frequency current from the tuned circuit to pulsing direct current to extract the audio modulation from the radio frequency carrier wave. The earphone E1 converts the audio current to sound waves.
- How a Crystal Radio Works (video 12:58) – Full details of how a crystal radio works, right down to the electron level. We start with a demonstration of all the parts in action, showing how the radio waves interact with the antenna and antenna coil to produce a fluctuating magnetic field, which induces electron flow in the tuning coil, which works with the tuning capacitor, which is followed by the diode and crystal earpiece.
- diagrams
- Crystal Radio – Directions for the construction of a simple-styled crystal radio.
- How to Make/Build a Crystal Radio (video 11:45) – Step-by-step instructions for making a tunable crystal radio. This is a radio that gets its power from the radio waves.
Additional related projects
- an amplifier that plays on a loud speaker
- a single transistor crystal radio amplifier that amplifies sound to the earpiece.
Engineering ideas
- crystal, radio, signal, antenna, coil, magnetic field, electron flow, capacitor, diode, power, amplifier, speaker, transistor
Do It
Challenges for you to work on…
- build a crystal radio following directions provided or search out other sites describing how to build your own crystal radio.
Learn more…
- Rimstar Org YouTube channel – science projects, explanations
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