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Armstrong Wasn’t the Only One

Who invented FM? Gary L. Frost offers a fresh exploration

An earlier version of this article misidentified the author of a biography of Edwin Armstrong. It is corrected here to Lawrence Lessing.

You probably know that Edwin H. Armstrong single-handedly invented frequency modulation, delivering a fully developed system in the early 1930s. Perhaps you also have heard that no one else was very much interested in FM, especially after John Carson, an AT&T engineer and FM naysayer, published an analysis in 1922 declaring that FM “inherently distorts without any compensating advantages whatever.”

You also know that Armstrong discarded existing preconceptions about narrowband FM when he began his experimentation, and moved right into wideband transmission as a means of eliminating static and delivering hi-fi audio to listeners. You probably believe too that RCA did everything possible to kill off FM, as it challenged the well-established RCA/NBC broadcasting empire.

According to Gary Frost, who’s both an historian and engineer, we’ve got it all wrong.

Ehret and friends

Frost has just published a fresh look at the genesis of frequency modulation — which, by the way, didn’t begin in the 1930s with work done by Armstrong at his Columbia University lab.

Frost’s “Early FM Radio: Incremental Technology in Twentieth-Century America” traces FM’s beginnings all the way back to 1902 and a patent application submitted by an obscure Philadelphia inventor, Cornelius Ehret.

Ehret described the use of FM for both radiotelegraphy and radiotelephony, and included circuitry for both FM transmission and reception. Frost’s research has unearthed a total of 83 FM patents filed between 1920 and 1934. Armstrong received his wideband FM patent near the end of 1933.

Frost’s investigation shows that while RCA had the lion’s share of these patents (44) — and actually was conducting on-air testing of FM as early as 1925 — GE, AT&T and Westinghouse (notably KDKA’s legendary Frank Conrad and others at that station) also were experimenting with this form of modulation.

The concept of the FM receiver “limiter” stage is shown to predate Armstrong’s wideband FM work, with Frost directing the reader’s attention to RCA’s Clarence Hansell and patents issued in 1927 and 1928.

The author notes that before the big “breakup” between Armstrong and RCA’s David Sarnoff in the mid-1930s, Armstrong was “almost an RCA employee” in terms of having access to radio research work at the company.

However, this was anything but a two-way street, as Armstrong was quite secretive about his own FM work. Frost states that “Armstrong clearly owed much to his [RCA] friends at Riverhead,” and that he applied knowledge of RCA’s successes and failures in his own work.

Frost sets right the comments of AT&T’s John Carson about FM’s ability to distort, and identifies Carson as the father of single-sideband modulation (something that Frost terms “probably more important than hi-fi FM”).

Fixing the record

“Early FM Radio” attributes many of the modern misconceptions about FM’s early history to biographer Lawrence Lessing and his posthumous tribute to Armstrong, published two years after the inventor’s plunge to his death on Jan. 31, 1954.

Lessing’s book, “Edwin Howard Armstrong: Man of High Fidelity,” is shown by Frost to be a less than accurate representation of the facts leading up to modern FM broadcasting, yet it became the “gold standard” concerning Armstrong and his achievements. (Lessing’s dissemination of misinformation has been compounded by later writers who accepted the account without question and echoed portions of it in their own works.)

Frost flags one of the most famous (yet spurious) incidents described by Lessing in connection with the first public demonstration of FM, which occurred on Nov. 6, 1935.

Armstrong had arranged for a close friend — Randy Runyon — to broadcast via FM from his Yonkers, N.Y. home to the audience assembled at an Institute of Radio Engineers meeting in Manhattan. In his 1956 book, Lessing described an elaborate battery of sound effects — water being poured, paper crumpled and torn, various forms of music — that were staged as part of the demonstration.

This is a schematic representation of Cornelius D. Ehret’s FM transmitter, shown in his 1905 patent ‘Art of Transmitting Intelligence,’ discussed in Frost’s book. The element at upper right, identified as #17, is a condenser microphone for instantaneously varying the transmitter’s frequency. Frost observes: “No one who attended that day reported hearing reproductions — vivid or otherwise — of crumpled paper, oriental gongs, guitars … Nor could they have, for Armstrong had yet to incorporate the ‘high fidelity’ circuits into his system that the reproduction of such sound effects requires.” Frost adds that this description of sound effects most likely came from a newspaper article that Lessing published some three-and-a-half years later.

While I maintain a deep respect for Major Armstrong and his many accomplishments, due to the investigative efforts of Frost I now have to temper that a bit with the reality that this well-documented history provides.

It’s been said many times that television was not invented by any one person; the same must now be said for FM broadcasting. While Armstrong played a large part, even personally funding the construction and operation of the world’s first FM radio station, Frost proves rather conclusively that he had company along the way in making wideband FM a reality.

“Early FM Radio” presents a refreshing new view of the development of FM radio, and one that is much overdue. It’s a must-read for those of us who have spent most of our lives believing that FM was a one-person invention.

I should note that Frost’s book is refreshing in another way. He breaks away from the current hertz, kilohertz and megahertz frequency designations, reverting to the “cycles,” “kilocycles” and “megacycles” that were in use at the time FM was being invented.

If I could change anything at all about Frost’s book, it would be the reproduction on Page 74 of three pages from a 1931 letter from RCA’s Hansell to Armstrong. These are compressed into a tiny space of 3.5 x 7.5-inches, making them almost illegible (especially to many of us who arrived on the scene in the decade of the 1930s, or the one immediately following).

Hopefully, future editions of Frost’s book will provide a little more real estate for these pages and eliminate the need to locate a high-power magnifier to understand why he included them.

“Early FM Radio: Incremental Technology in Twentieth-Century America” is published by the Johns Hopkins University Press.

James O’Neal is technology editor for TV Technology magazine and a frequent contributor to Radio World. He wrote about Mary Day Lee in our May 5 issue.