Invention History: The Father of FM

State-of-the-Art Reception

While stationed in France, Armstrong achieved a spectacular new radio breakthrough: the superheterodyne receiver, a high-performance radio receiver incorporating a variable oscillator. it made everything that came before - including his own regenerative receiver - obsolete.

The basic superheterodyne configuration continues to be used today in most radio and television receivers, as well as in cellular phones, and other communication devices.

While in Europe, the French government gave Armstrong the use of the Eiffel Tower for his radio experiments. He was also named a Chevalier de la Legion d'Honneur - a prestigious award established by Napoleon Bonaparte' in 1802 - to honor his radio work.

Armstrong received the patent for his superheterodyne receiver in 1920. He sold that, as well as another for a superegenerative receiver, becoming a millionaire in the process. By 1923, he was wealthy enough to accept a faculty position without salary at Columbia. The position allowed him to concentrate on research without the dual distractions of teaching or administrative duties, and Columbia was happy to have him.

About this time, Armstrong and Sarnoff embarked on a mutually beneficial business arrangement. RCA was able to use Armstrong's licenses to pursue Sarnoff's goal of achieving a dominant position within a new industry, on the manufacturing, as well as the broadcasting end of things.

For Armstrong, the relationship was professionally, as well as personally rewarding.

Sarnoff was a benefactor with very deep pockets. And within a decade, it would net Armstrong access to the top of the Empire State Building, the world's tallest antenna platform for his experiments.

Armstrongs with First "Portable" RadioArmstrongs with First "Portable" RadioFor the personal benefits, Sarnoff had a secretary named Marion MacInnis. She became Marion Armstrong.

Marion has been described as "a woman with plenty of understanding for her driven husband." It was a good match.

Not everything, however, was going along smoothly for Armstrong. The see-saw battle over regeneration continued. Lower courts found in Armstrong's favor a number of times, but still the case dragged on. Finally in 1934, the United States Supreme Court ruled in favor of DeForest's claim for precedence. The decision was condemned by Armstrong's colleagues in the scientific community, who blamed it on the court's lack of understanding of technical issues.

It was the end of the line for Armstrong and regeneration. All he could do was move on. Before that, however, he attempted to bring closure by doing what seemed, to him, the right thing to do.

Armstrong attended the IRE convention in 1934, where he tried to return the Medal of Honor that body had given him in 1934 for regeneration. The convention refused to accept the return of the award, and gave him a standing ovation instead.

DeForest was recognized as the inventor of regeneration as a result of a Supreme Court decision handed down more than two decades after its initial discovery and development. In fact, DeForest's rightful claim to ownership of the technology was accepted by very few beyond DeForest and AT&T, who had financial incentives for doing so.

For the most part, Armstrong's colleagues continued to give him full credit for regeneration. In 1941, the Franklin Institute gave him the Franklin Medal. In 1942, the American Institute of Electrical Engineers (AIEE) presented him with the Edison Award. Named for Thomas Alva Edison, the first recipient in 1904, the Edison Award is the engineering profession's oldest and most prestigious honor.

A year before the Supreme Court allowed DeForest to break his regeneration patent, Armstrong achieved his greatest radio triumph: Frequency Modulation (FM).


Back in the '20s, FM had been unsuccessfully attempted by others. Ironically, it was an AT&T scientist, John Carson, who performed an analysis that concluded that the format offered no substantial advantages over Amplitude Modulation, AM, radio. Based on the publication of a learned opinion rejecting FM's viability, the whole of the scientific community accepted Carson's pronunciation as proof. Game, set, match.

The whole of the scientific community accepted the unassailability of Carson's opinion except Armstrong.

AM worked by varying the strength, or amplitude of the broadcast signal. AM is inherently noisy because it is compatible with a multitude of other, natural signals in the atmosphere, which are, in turn, heard as static.

On the other hand, FM works by varying the frequency of the signal, making the medium compatible with few other naturally-generated sounded in the atmosphere. The result is much cleaner, less static-filled.

Armstrong had a prototype of his new FM system working in 1933. As a matter of course, he approached RCA, who already had most of his licenses.

RCA rejected Armstrong's offer, and his contention that consumers would flock to the new medium because of its superior sound quality. Actually, RCA was heavily invested in AM for both broadcasting (National Broadcasting Corporation, NBC) and manufacturing. It stood to lose a bundle if it abandoned AM for FM.

Undeterred, Armstrong moved ahead with the development of his new project. In 1934, he filed a series of patent applications. By 1935, he was ready to present it to the public.

The unveiling of FM took place at the 1935 IRE convention. Audience members were treated to a program - broadcast from the house of one of Armstrong's friends in Yonkers - consisting of music and various different sounds. The sound of pouring water and paper being torn were clearly recognizable. They would have been indecipherable over AM.

David Sarnoff hoped the demonstration would provoke a call for research into improving the sound quality of AM. Instead, Armstrong's exhibition clearly demonstrated FM's superiority over AM, and threatened to overthrow established order for big broadcasting.

Sarnoff, however, was not prepared to just roll over.

For his part, Armstrong was convinced that FM could succeed on the strength of its merits alone. Around this time he said FM had nothing to fear but "those intangible forces so frequently set in motion by men, and the origin of which lies in vested interests, habits, customs, and legislation."

It was an eerily prophetic vision of things that were about to happen.

Apr 15, 2007
by Michelle
Michelle's picture

Mike, Is FM used for


Is FM used for anything else but radio? Is the inventor of FM inventor of FM radio?

Apr 16, 2007
by Mike (not verified)

Yes, EH Armstrong is

Yes, EH Armstrong is considered the inventor of FM. It's used a lot outside of radio. TV  sound is FM. Military, NASA. Cellphones sound technology is based on it. 


Jul 6, 2008
by Anonymous