Engines of Our Ingenuity

No. 317:
EDWIN ARMSTRONG AND FM RADIO

by John H. Lienhard

Click here for audio of Episode 317.

Today, a teenager decides to do something important. 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.

Edwin Armstrong was born in 1890. When he was 15 he read The Boy's Book of Inventions and straightaway declared he'd be an inventor of radios. Radio was then younger than he was, and he dove right in. Seldom is a decision to do something worthwhile so clear-cut. Eight years later, Armstrong demonstrated his new regenerative feedback circuit. He massed the engineers of the American Marconi Company in a room at Columbia University. There he proved he could pick up signals from Ireland by rewiring a standard radio tube.

Armstrong was big and athletic. He played tennis with hungry intensity. He raced automobiles. He climbed mountains. And when he couldn't do that he climbed radio towers. As a young major in the WW-I Air Service, he developed aerial radio systems.

He thought he could track an airplane by reading the electric signal of its ignition. That set the stage for a major conceptual leap. He saw that he could mix an incoming radio signal with an imposed signal and produce a new signal with a frequency that was easier to amplify.

He went on to spin that technology into FM radio. By 1933 he was able to show a practical FM system to his old friend, David Sarnoff, president of RCA. Sarnoff experimented with the new technique but in the end abandoned it because it meant too radical a change in radio systems. Armstrong finally launched his own FM system. He himself didn't fare as well as FM radio did. After WW-II he fell into a quicksand of lawsuits with RCA over FM patent rights.

Armstrong met his wife-to-be, Marion MacInnis, in 1923. He wooed her in odd ways. He drove her about in fast cars. He scaled the 450-foot RCA transmitter tower for her. He gave her the first portable superheterodyne radio for a wedding present. Twenty years later, his youthful verve caved in as he swam in losing legal battles. He gave up. He wrote Marion a sad letter apologizing for what he was about to do. Then he scaled his last height and jumped ten stories to his death.

His wife had greater conviction than he did. She stayed the course and won the final patent victory for him in 1967. Today you're probably hearing me on FM radio. Indeed, FM lets you hear far prettier sounds than any I might make. And it all flows from Edwin Armstrong's teenage certainty that he could scale the mountain, win the prize, and give the world something good and new.

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

(Theme music)


Lewis, S.W., Radio Revolutionary. American Heritage of Invention and Technology, Vol. 1, No. 2, 1985, pp. 34-41.


The Engines of Our Ingenuity is Copyright © 1988-1997 by John H. Lienhard.


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