How to Make a Crystal Radio in 10 Minutes

A crystal radio can receive AM broadcasts from hundreds of miles away..

Crystal radios were among the first radio receivers built and sold. Their simple construction allowed American soldiers in World War II to build them in foxholes, giving crystal radios the name 'foxhole radios.' Crystal radios require no power to operate, but are able to receive AM radio broadcasts from hundreds of miles away. The simplicity of a crystal radio means you can build one in a matter of minutes with few or no tools.

Things You'll Need

• Wooden pencil
• Spool of #30 magnet wire
• Germanium diode
• Ear bud headphones
• Thin half-inch hex nut
• Electrical tape

Instructions

1. Cut 50 feet of magnet wire. Magnet wire is coated in an insulated enamel that must be removed to make an electrical connection. Scrape a quarter inch of enamel of the end of the wire. Wrap the magnet wire around the pencil leaving the bare end close to the eraser end.

2. Cut one ear bud from the set of headphones. Leave as much wire attached to the ear bud as possible. Strip the end of the wire attached to the ear bud. There are two conductors in the ear bud wire. Tape the diode to one conductor. Attach the diode so the marked end is pointed away from the ear bud. Tape the conductor to the hex nut.

3. Cut 10 feet of magnet wire for the ground connection. Strip the enamel from both ends. Tape one end of this wire to the hex nut.

4. Cut a 3 foot length of wire for the antenna. Scrape the enamel from one end. Tape this wire, the free end of the diode and the wire wound around the pencil to the eraser clip.

5. Slide the hex nut over the coil of wire wrapped around the pencil several times. Sliding the nut will scrape the insulation off of the wire, providing an electrical contact. Attach the loose end of the ground connection to a faucet, radiator or other metal plumbing fixtures with tape.

6. Listen to the radio through the ear bud. If you do not hear anything, slide the nut over the pencil. The frequency of the radio is determined by where the nut is on the coil of wire.

Tips & Warnings

• Crystal radios do not have amplifiers. Because of this, the audio received is not very loud. Listen to the crystal radio set in a quiet setting.

• Attach a longer antenna if the volume is insufficient.

References

• Crystalradio.net: Crystal Radio Plans and Circuits
• Bizarrelabs.com: Foxhole and POW Built Radios: History and Construction

Resources

• Read this Article in Spanish