Crystal radios are simple devices. The components are a coil (inductor), a detector (germanium diode), a tuning capacitor, a headphone, and an antenna. There are many variations, as you will see. These radios receive AM medium wave frequencies, and in some cases, the higher shortwave frequencies as well. (MW 500-1750 KHz SW 1750 KHz- 30 MHz)
This crystal radio is the classic design with a variable inductor, a tuning capacitor, a germanium diode detector, and a resistor. The radio is hooked up to a 30' or longer wire for the antenna, and is also grounded. The radio is capable of receiving most strong local AM stations during the day, and can also receive more distant stations and even shortwave stations at night.
This little crystal radio is a variation. Instead of a tuning capacitor, it uses a ferrite rod that slides in and out of the coil to select stations. It is quite sensitive when connected to a good antenna and ground, but is not good for shortwave reception. I built this one into a little plastic box with a hinged lid- very portable.
This hybrid design is perhaps my favorite. The computer ribbon cable is joined to form the coil. It's just a measured length of computer cable that is joined at the ends, but staggered by one wire so that it forms a continuous coil of wire. Because of its diameter and precise number of coil windings it is very sensitive without requiring an additional antenna or ground. So this floppy contraption can then be suspended to form a big loop. The tuning capacitor tunes in the stations. In addition, the loop can be aimed to further tune in or tune out a particular broadcast station.
RIBBON CABLE PLANS
Parts and instruction for the building of crystal radios are available at your Radio Shack type stores. If you are interested in learning more about these magic "low tech" radios you can visit my friends, The Crystal Radio Society at the link below. They have books, plans, parts, and even kits.
SOLAR COOKING PAGES
Back to Journey to Forever Schools participation
Journey to Forever Home