Can You Really Build Your Own Radio?

By Earl Hunsinger

When you were a kid, did you ever build a telephone from a long piece of string and a couple of paper cups? Believe it or not, it is only a little harder to build your own radio. But wait, aren’t radios incredibly complicated pieces of technology with hundreds of components arranged in sophisticated electronic circuits? Yes, they are, just like telephones. Yet, like telephones, the basic scientific principles behind radios can be demonstrated by putting together a few simple components. In fact, like your paper cup telephone, it is even possible to make a crude radio from household items. Some can be made from as little as two parts.

Like the energy we receive from the sun, radio waves are a form of electromagnetic radiation. In most places (don’t panic), we are constantly being bombarded by this radio wave radiation. We take this for granted when we turn on our walkman or other portable radio. The term electromagnetic is used because there is a relationship between electricity and magnetism. Electricity can be used to create a magnet and a magnet can be used to create electricity. Another fun project that many kids have tried involves wrapping a length of wire around a nail and connecting it to a small battery to make an electromagnet. It’s also possible to move a magnet across a wire and make electricity flow in the wire. For more information on radio waves and electromagnetic radiation in general, see the Northwestern University Qualitative Reasoning Group page dealing with How Nasa Communicates with Spacecraft.

Radio waves carry electromagnetic energy. When they hit the antenna of our radio they make a tiny amount of electricity flow in it. This electricity carries the "signal," the music or voices transmitted from the radio station. Any piece of metal can act like an antenna; when the radio waves hit it, electricity flows through the metal. You don’t have to worry about getting shocked by this electricity because it is a very small amount. The trick to making a radio work, any radio, involves using this small amount of electricity to make sound.

If you are old enough you may remember the days when portable radios had telescoping antennas. The idea was that as the piece of metal used for the antenna increased in length, more electricity would flow through it. As more electricity flowed through it, the radio reception would improve. With the invention of more and more sensitive electronics, many modern radios have eliminated the use of such bulky and visible antennas.

When building your own radio, without the use of such modern electronics, a good antenna is once again an essential component. A long wire works very well as an antenna. Although most radio stations use tens of thousands of Watts to transmit their signals, unless we are very close, we can capture only a very small amount of this energy. As stated on the website Science Toys, even with an antenna hundreds of feet long, you may only get a few billionths of a Watt flowing through your wire. The reason that a homemade radio can work is that the human ear is capable of detecting sounds with energy a million times smaller than even this small amount.

The website Science Toys, mentioned above, gives detailed instructions for building a homemade radio with a long piece of wire, a simple and inexpensive electronic component (a germanium diode) purchased from an electronics store, and a telephone handset. It also contains some fascinating information about building your own electronic components out of household items.

America Online has a good article about the simple radios that soldiers built in foxholes during World War II. They used these to listen to "jive" programs, along with some propaganda, transmitted from an Axis radio station in Rome. The article also contains some pictures and schematics allowing you to build your own "foxhole radio."

Finally, The Xtal Set Society is a whole website devoted to building your own radios, normally referred to as crystal, or Xtal, sets. This site has books, parts, plans, kits, and an abundance of helpful information.

Since the beginning of radio communication, people have been experimenting. There was a time when it was necessary to build your own equipment if you wanted to be involved with amateur radio. This is no longer the case. Whatever your interest in radio, there is now equipment available that is much better than most of us could ever hope to build ourselves. Yet by building a simple homemade radio you may be able to capture and experience for yourself some of the excitement that must have filled those early radio pioneers. You may also find that you gain knowledge and a sense of satisfaction that you could never acquire in any other way.