Frost, Gary L. Early FM Radio: Incremental Technology in Twentieth-Century America. Baltimore:  The Johns Hopkins University Press, 2010. Pp. xi plus 191. Hardcover, $48.35.

Frost presents another perspective on the story of how FM radio broadcasting came into being—an antidote, if you will, to the story presented by the Ken Burns documentary Empire of the Air or in the book by Lawrence Lessing,Edwin Howard Armstrong: Man of High Fidelity  (Philadelphia: J. B. Lippincott, 1956). The first part of the present book describes early work, before 1920, beginning with a frequency shift keying system developed in 1902 by Cornelius Ehret and the arc-oscillator of the well-known Valdemar Poulsen.  (It seems to me that frequency shift keying bears the same relationship to FM broadcasting as Morse code does to AM.)This part includes a short review of the principles of modulation and broadcasting.  The second part of the book is basically a recounting of Armstrong’s dealings with RCA.  RCA licensed Armstrong’s regeneration and superheterodyne circuits in 1922, and in return Armstrong became a very large shareholder in RCA.  He also signed a first refusal agreement with RCA covering future patents, which gave Armstrong access to the FM related technical work taking place at RCA, and also at AT&T, GE, and Westinghouse which shared a patent pool.  Frost implies such access was of significant value to Armstrong. Frost further states that Armstrong generally did not share his own work. Armstrong worked basically independently and first demonstrated his system in 1934.  RCA, however, elected not to pursue FM.  Frost believes the RCA decision was based on the inconclusiveness of the demonstration, although one could argue it was simply “Not Invented Here.”  Armstrong went on to make impressive public demonstrations, and FM was picked up by other radio manufacturers.  

Two of the reasons FM appeared attractive were anti-fading and noise reduction.  An argument for noise reduction was that the FM carrier frequencies would be much higher than that used for AM, and noise was believed to be less at higher frequencies.  Mathematical analysis at AT&T had shown early that narrow band FM did not offer noise discrimination.  An argument against wide band FM was that the wider band allowed more noise into the receiver, but the wide band system ultimately perfected by Armstrong showed nearly noise (static) free reception—the reason FM is used so commonly now.

Early FM Radio is marred for me by unsubstantiated statements about Armstrong’s beliefs and insights.  Armstrong evidently made contradictory statements over the course of his research about whether wideband FM would eliminate static.  On that basis Frost claims Armstrong serendipitously fell into his successful FM broadcasting system.  A full transcript of what Armstrong actually said would have been helpful in supporting the claim.  An electrical engineering colleague pointed out several technical errors in the book.  The book does include references to various approaches to the sociology of technology. Early FM Radio is probably of most interest to someone already familiar with the history, and the text may suggest important questions.  People without such familiarity are probably better off starting elsewhere—for example, the Lessing book or the Burns documentary noted above.  These also give a picture of the complex and tragic person who was E. H. Armstrong.