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
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. That was a powerful combination.
It was rare to have more than one radio in any
1930s house, 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 was
tricky. You could build your own crystal
set. That was a primitive radio whose heart
was a polycrystalline lump of galena, set in lead.
The crystal worked as a rectifier. It served in
place of a radio tube. Today, a transistor serves
you'd made the set, you pecked away at the surface
of the crystal with a fine wire probe called a
cat's whisker. You eventually hit just the
right facet of the crystal -- one that responded to
the station you'd tuned on a homemade coil.
The signal was weak. There was no amplifier. You
listened to it with earphones. But with your own
secret crystal set, you'd be able to pull the
covers over your head and listen to your heart's
content -- after your mother had 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. You never quite managed to make
your own radio -- one you could play under the
bed-covers. In the end, you were left reading comic
books with a flashlight.
Radio permeated American life with amazing speed
after its invention at the turn of the twentieth
century. Here's a 1924 book, typical of the times,
called The Boy Scientist. It has a
twenty-eight-page chapter on radio-building.
The first section is titled, How to Make a
Cheap Crystal Receiving Set. You'll have to
pay two dollars for earphones. And the radio's
performance will be improved if you buy a condenser
to put across the headphone
terminals. A finished
coil can be bought for three dollars, or you
can wind your own coil at the cost of about a
dollar. The second section of the chapter tells how
to make a better set. Cost and complexity begin
You want to scream, Stop! Even that simple
set is the business of fourteen-year-olds. And you
are only nine.
Making a radio was far easier to dream
than it was to do. So you dreamt and
wished. Of course, that wish actually came true.
Today we can let Franz Schubert or Arvo Pärt
wash us into slumber. But, oh, it wouldn't it've
been something to've made one of those
temperamental crystals sing you to sleep -- when
you were nine years old.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
I am grateful to Owen Pool for calling my attention
to his excellent web site with all kinds of
information on crystal sets: http://www.thebest.net/wuggy/
Collins, A. R., The Boy Scientist. Boston:
Lothrop, Lee, & Shepard Co., 1925. (All images
displayed or linked on this page are from this
This is a greatly revised version of Episode 176.
Neil Boucher writes in to warn readers of this
website about this circuit diagram from The Boy
Scientist. It shows, he says, "the all too
common practice of having separate grounds for
lighning conductors and other devices. This is very
dangerous." The diagram implicitly shows three
grounds: the crystal set, the lightning rod and the
household ground. "At the time of a strike to any of
the grounds, all three will be at different
potentials," and that can be deadly. "In fact people
get shocked by using a phone during an electric storm
because the grounding at the telephone switch is
not bonded to the household ground (except
via the earth itself). And this allows dangerous
potentials to build up."
When this episode from 2002 reran on Jan. 9, 2011, I received an email pointing to
a source that still provides crystal sets, a century later. see
The Engines of Our Ingenuity is
Copyright © 1988-2002 by John H.