Build a Crystal Radio
Build a radio that needs no batteries - powered entirely by radio waves!
Overview
The crystal radio is the simplest possible receiver. It was how many engineers first got interested in electronics. With a good antenna, you can hear local AM stations!
Components Needed
- 1x Germanium diode (1N34A)
- 1x Variable capacitor (10-365pF)
- 50 feetx Magnet wire (22-26 AWG)
- 1x Cardboard tube (toilet paper roll)
- 1x High impedance earphone (crystal/ceramic)
- 50+ feetx Antenna wire
- 10 feetx Ground wire
Instructions
Wind the Coil
Wind about 60-80 turns of magnet wire on the cardboard tube. This forms the inductor. Leave about 6 inches at each end for connections. Scrape the enamel off the ends.
Assemble the Tuner
Connect the variable capacitor in parallel with the coil. This LC circuit resonates at the station frequency. Tuning the cap selects different stations.
Add the Detector
Connect the germanium diode from the top of the LC circuit. The diode rectifies the RF signal, extracting the audio modulation.
Connect Antenna and Earphone
Attach antenna to top of coil, ground to bottom. Connect earphone from diode output to ground. Find a quiet room and tune carefully!
Challenges
- Optimize your antenna for best reception
- Add a tap on the coil for better matching
- Build a more selective double-tuned version