Edwin Howard Armstrong (December 18, 1890[2] – February 1, 1954[3]) was an American electrical engineer and inventor who developed FM (frequency modulation) radio and the superheterodyne receiver system.

At the age of eight, Armstrong contracted Sydenham's chorea (then known as St. Vitus' Dance), an infrequent but serious neurological disorder precipitated by rheumatic fever.

[10] He loved heights and constructed a makeshift backyard antenna tower that included a bosun's chair for hoisting himself up and down its length, to the concern of neighbors.

In 1934, he filled the vacancy left by John H. Morecroft's death, receiving an appointment as a professor of Electrical Engineering at Columbia, a position he held the remainder of his life.

[17] His breakthrough discovery was determining that employing positive feedback (also known as "regeneration") produced amplification hundreds of times greater than previously attained, with the amplified signals now strong enough so that receivers could use loudspeakers instead of headphones.

Beginning in 1913 Armstrong prepared a series of comprehensive demonstrations and papers that carefully documented his research,[18] and in late 1913 applied for patent protection covering the regenerative circuit.

[23] In response to the second Supreme Court decision upholding de Forest as the inventor of regeneration, Armstrong attempted to return his 1917 IRE Medal of Honor, which had been awarded "in recognition of his work and publications dealing with the action of the oscillating and non-oscillating audion".

Later that year Armstrong was commissioned as a captain in the U.S. Army Signal Corps, and assigned to a laboratory in Paris, France to help develop radio communication for the Allied war effort.

AT&T, interested in radio development at this time, primarily for point-to-point extensions of its wired telephone exchanges, purchased the US rights to Lévy's patent and contested Armstrong's grant.

While he was preparing apparatus to counteract a claim made by a patent attorney, he "accidentally ran into the phenomenon of super-regeneration", where, by rapidly "quenching" the vacuum-tube oscillations, he was able to achieve even greater levels of amplification.

"Static" interference – extraneous noises caused by sources such as thunderstorms and electrical equipment – bedeviled early radio communication using amplitude modulation and perplexed numerous inventors attempting to eliminate it.

In 1922 John Renshaw Carson of AT&T, inventor of Single-sideband modulation (SSB), had published a detailed mathematical analysis which showed that FM transmissions did not provide any improvement over AM.

In 1931 the RCA engineers constructed a successful FM shortwave link transmitting the Schmeling–Stribling fight broadcast from California to Hawaii, and noted at the time that the signals seemed to be less affected by static.

From May 1934 until October 1935 Armstrong conducted field tests of his FM technology from an RCA laboratory located on the 85th floor of the Empire State Building in New York City.

[35] Denied the marketing and financial clout of RCA, Armstrong decided to finance his own development and form ties with smaller members of the radio industry, including Zenith and General Electric, to promote his invention.

Armstrong thought that FM had the potential to replace AM stations within 5 years, which he promoted as a boost for the radio manufacturing industry, then suffering from the effects of the Great Depression.

A United Press correspondent was present, and recounted in a wire service report that: "if the audience of 500 engineers had shut their eyes they would have believed the jazz band was in the same room.

Armstrong was quoted as saying he could "visualize a time not far distant when the use of ultra-high frequency wave bands will play the leading role in all broadcasting", although the article noted that "A switchover to the ultra-high frequency system would mean the junking of present broadcasting equipment and present receivers in homes, eventually causing the expenditure of billions of dollars.

"[39] In the late 1930s, as technical advances made it possible to transmit on higher frequencies, the FCC investigated options for increasing the number of broadcasting stations, in addition to ideas for better audio quality, known as "high-fidelity".

One area of concern was the effects of tropospheric and Sporadic E propagation, which at times reflected station signals over great distances, causing mutual interference.

Article placements promoting both Armstrong personally and FM were made with general circulation publications including The Nation, Fortune, The New York Times, Atlantic Monthly, and The Saturday Evening Post.

Outraged by this, in 1948 Armstrong filed suit against RCA and the National Broadcasting Company, accusing them of patent infringement and that they had "deliberately set out to oppose and impair the value" of his invention, for which he requested treble damages.

Although he was confident that this suit would be successful and result in a major monetary award, the protracted legal maneuvering that followed eventually began to impair his finances, especially after his primary patents expired in late 1950.

Armstrong hoped that the interference fighting characteristic of wide-band FM and a narrow receiver bandwidth to reduce noise would increase range.

Bitter and overtaxed by years of litigation and mounting financial problems, Armstrong lashed out at his wife one day with a fireplace poker, striking her on the arm.

[3] Sometime during the night of January 31 – February 1, 1954, Armstrong jumped to his death from a window in his 12-room apartment on the 13th floor of River House in Manhattan, New York City.

[54] The New York Times described the contents of his two-page suicide note to his wife: "he was heartbroken at being unable to see her once again, and expressing deep regret at having hurt her, the dearest thing in his life."

Senator Joseph McCarthy (R-Wisconsin) reported that Armstrong had recently met with one of his investigators, and had been "mortally afraid" that secret radar discoveries by him and other scientists "were being fed to the Communists as fast as they could be developed".

The hall, located at the northeast corner of Broadway and 112th Street, was originally an apartment house but was converted to research space after being purchased by the university.

A second Armstrong Hall, also named for the inventor, is located at the United States Army Communications and Electronics Life Cycle Management Command (CECOM-LCMC) Headquarters at Aberdeen Proving Ground, Maryland.