How to Make a Transistor Radio

Learn how to make a radio that is powered by little more than a penny.

| January/February 1982

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    This blueprint shows the circuitry of the penny-powered radio.
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    The penny-powered radio.

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With the ever-decreasing purchasing power of the dollar, you'll probably be relieved to know that even the smallest coin of the realm still has some value. Yep, a penny will provide the same power today as it did a hundred years ago. Now I'm not announcing the end of inflation . . . but the fact of the matter is that a single red cent will power a one-transistor radio!

Better yet, this particular radio can be constructed almost entirely from materials found around the average homestead or apartment. And don't be discouraged if you lack one or more of the specified items. By using your imagination and ingenuity, you'll likely be able to find a reasonable facsimile . . . and your scavenging can result in a bona fide homemade AM radio!

Building a Radio

A section of pine board — about 9-foot square — will provide a good foundation for your scrap-box project. You can stain or carve or engrave (use whatever talent you might have) the wooden base to your liking. After doing so, seal it with a couple of coats of varnish.

Constructing the coil will be the most demanding task. It's not really all that difficult, but it is time consuming. To assemble this component, locate a cardboard tube (like those that paper towels come on), and cut off a piece about six inches long. This will serve as the form for the coil.

The cylinder must then be wound with an enamel-covered copper wire, about 28 AWG. I obtained mine by carefully unwinding a solenoid rescued from a defunct eight-track tape player (it's used in the mechanism for changing tracks). However, any motor, doorbell or similar electromagnetic device will probably give you as much of the required wire as you'll need. (For those of you who are unfamiliar with the AWG system of wire gauging, 28-AWG wire is 0.013-inch in diameter. You can measure it with calipers or with a micrometer. Gauges 24 — 0.020-inch — through 28 are all quite acceptable for this project.)

Poke a hole in the tube at a point 1/2 inch from the end and another hole, in line, 1/2 inch from the first. Thread the free end of the enamel-covered wire through the second hole into the tube. Then run it back out through the first hole, allowing six inches to protrude, and pull it taut in order to prevent the wire from unraveling.

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