Today, we try to make a radio. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

How I grooved on stories and daydreams when I was nine years old! And radio provided them. Radio gave us the words, our minds drew the pictures, and that was a powerful combination.

It was rare to have more than one radio in a house in the 30s, and you listened to it when your parents said you could. But listening always ended too soon. You were always called away -- to school, to supper, to chores, and to bed.

There was a way around the problem, but it wasn't easy. You could build your own crystal set. That was a simple primitive radio whose heart was a polycrystalline lump of galena, set in lead. The crystal worked as a rectifier -- in place of a radio tube. You pecked away at its surface with a fine wire probe called a cat's-whisker. Sooner or later you hit just the right facet of the crystal -- one that responded to the station you'd set on a home-made coil.

The signal was weak. There was no amplifier. You listened to it with earphones. But with your own crystal set, you'd be able to pull the covers over your head and listen to your heart's content -- after your mother'd said good night. You'd be able to listen to music, or I Love a Mystery, and no one would know.

Mechanics Illustrated or any of a hundred how-to-do-it books all explained, in formidable detail, how to make a crystal set from hardware-store parts. But you were nine years old, and something always went wrong -- a loose wire, a badly wound coil. So you never quite figured out how to make your own radio to play under the bed-covers. In the end you were left reading comic books with a flashlight.

The radio permeated American life with amazing speed after its invention at the end of the nineteenth century. Here's an old Boy Scout manual, published just a few years later -- in 1910. It tells you how to earn a merit badge in Radio. You had to draw the complete circuit diagram for a receiver set -- from memory. You also had to build your own set, using a tube -- not a crystal. Then you had to pick up a signal 25 miles from a transmitter. Of course, all that was for 14-year-olds.

But you were only nine, and making a radio was far easier to dream about than to do. So you dreamt and wished. Of course, that wish actually came true. Today you can let Dvorak and Britten wash you into slumber. But I still wish I could have made one of those temperamental crystals sing me to sleep.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

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This episode has been greatly revised as Episode 1695.

The crystal set advertisement from a 1930s Sears Roebuck Catalog