Edwin Howard Armstrong

Edwin Howard Armstrong
Edwin H. Armstrong

Developed and advanced the utility of FM technology.
Born December 18, 1890(1890-12-18)
New York, New York U.S. [1]
Died January 31, 1954(1954-01-31) (aged 63)
New York (Manhattan), New York, U.S.
Education Columbia University
Occupation Electrical engineer
Known for Inventor of FM radio
Spouse Marion MacInnis (1922–1954) (his death)

Edwin Howard Armstrong (December 18, 1890 – January 31, 1954) was an American electrical engineer and inventor. Armstrong was the inventor of modern frequency modulation (FM) radio.

Edwin Howard Armstrong was born in New York City, New York, in 1890. He studied at Columbia University where he was a member of the Epsilon Chapter of the Theta Xi Fraternity. He later became a professor at Columbia University. He invented the regenerative circuit while he was an undergraduate and patented it in 1914, followed by the super-regenerative circuit in 1922, and the superheterodyne receiver in 1918.[2][3]


Early life

Armstrong in WWI signal corps uniform

Armstrong was born in the Chelsea district of New York City to John and Emily Armstrong.[1] In 1902 the family moved to Yonkers. Armstrong showed an interest in electrical and mechanical devices, particularly trains, from an early age.[4]

He loved heights and constructed a makeshift radio antenna tower in his back yard. Swinging on a bosun's chair, he would hoist himself up and down the tower to the concern of his neighbors. A case of rheumatic fever as a child left him with a tic in one eye.

In late 1917, Armstrong was invited to join the U.S. Army Signal Corps with the rank of captain and was sent to Paris to help set up a wireless communication system for the Army. He returned to the United States in the fall of 1919.[4]

During his service in both world wars, Armstrong gave the U.S. military free use of his patents. Use of these was critical to the Allied victories.

Unlike many engineers, Armstrong was never a corporate employee. He performed research and development by himself and owned his patents outright. He did not subscribe to conventional wisdom and was quick to question the opinions of his professors and his peers.

Work and patent disputes

Armstrong's "feed back" circuit drawing, from Radio Broadcast vol. 1 no. 1 1922.

Edwin Armstrong contributed the most to modern electronics technology. His discoveries revolutionized electronic communications. Regeneration, or amplification via positive feedback is still in use to this day. Also, Armstrong discovered that Lee De Forest's Audion would go into oscillation when feedback was increased. Thus, the Audion could not only detect and amplify radio signals, it could transmit them as well.

While De Forest's addition of a third element to the Audion (the grid) and the subsequent move to modulated (voice) radio is not disputed, De Forest did not put his device to work. Armstrong's research and experimentation with the Audion moved radio reception beyond the crystal set and spark-gap transmitters. Radio signals could be amplified via regeneration to the point of human hearing without a headset. Armstrong later published a paper detailing how the Audion worked,[5] something De Forest could not do. De Forest did not understand the workings of his Audion.

Armstrong's discovery and development of superheterodyne technology made radio receivers, then the primary communications devices of the time, more sensitive and selective. Before heterodyning, radio signals often overrode and interfered with each other. Heterodyning also made radio receivers much easier to use, rendering obsolete the multitude of tuning controls on radio sets of the time. The superheterodyne technology is still used today.

Armstrong is possibly best known for his discovery of wide-band frequency modulation. FM was born of a request by David Sarnoff of RCA as a means to eliminate static in radio reception. While Sarnoff was understandably impressed with Armstrong's FM system, he also understood that it was not compatible with his own AM empire. Sarnoff came to regard FM as a threat and refused to support it any further.

Many of Armstrong's inventions were ultimately claimed by others in patent lawsuits. In particular, the regenerative circuit, which Armstrong patented in 1914 as a "wireless receiving system," was subsequently patented by Lee De Forest in 1916; De Forest then sold the rights to his patent to AT&T. Between 1922 and 1934, Armstrong found himself embroiled in a patent war, between himself, RCA, and Westinghouse on one side, and De Forest and AT&T on the other. At the time, this action was the longest patent lawsuit ever litigated, at 12 years. Armstrong won the first round of the lawsuit, lost the second, and stalemated in a third. Before the Supreme Court of the United States, De Forest was granted the regeneration patent in what is today widely regarded as a misunderstanding of the technical facts by the Supreme Court justices.[6]

By early 1923, however, Armstrong was a millionaire as a result of licensing his patents to RCA.[4]

In 1946 the FCC's decision to use Armstrong's FM system as the standard for NTSC television sound gave Armstrong another chance at royalty payments. However, RCA refused to pay him royalties and encouraged other television makers not to pay them either.

FM radio

Columbia's Philosophy Hall. Armstrong developed FM radio in its basement laboratory.

Even as the regenerative-circuit lawsuit continued, Armstrong was working on another momentous invention. While working in the basement laboratory of Columbia's Philosophy Hall, he created wide-band frequency modulation radio (FM). Rather than varying the amplitude of a radio wave to create sound, Armstrong's method varied the frequency of the wave instead. FM radio broadcasts delivered a much clearer sound, free of static, than the AM radio dominant at the time. (Armstrong received a patent on wide-band FM on December 26, 1933.[7]

In 1922, John Renshaw Carson of AT&T, inventor of Single-sideband modulation (SSB modulation), had published a paper in the Proceedings of the IRE arguing that FM did not appear to offer any particular advantage.[8] Armstrong managed to demonstrate the advantages of FM radio despite Carson's skepticism in a now-famous paper on FM in the Proceedings of the IRE in 1936,[9] which was reprinted in the August 1984 issue of Proceedings of the IEEE.[10]

Today the consensus regarding FM is that narrow band FM is not so advantageous in terms of noise reduction, but wide band FM can bring great improvement in signal to noise ratio if the signal is stronger than a certain threshold. Hence Carson was not entirely wrong, and the Carson bandwidth rule for FM is still important today. Thus, both Carson and Armstrong ultimately contributed significantly to the science and technology of radio. The threshold concept was discussed by Murray G. Crosby (inventor of Crosby system for FM Stereo) who pointed out that for wide band FM to provide better signal to noise ratio, the signal should be above a certain threshold, according to his paper published in Proceedings of the IRE in 1937.[11] Thus Crosby's work supplemented Armstrong's paper in 1936.

Armstrong conducted the first large scale field tests of his FM radio technology on the 85th floor of RCA's (Radio Corporation of America) Empire State Building from May 1934 until October 1935. However RCA had its eye on television broadcasting, and chose not to buy the patents for the FM technology.[12] A June 17, 1936, presentation at the Federal Communications Commission (FCC) headquarters made headlines nationwide. He played a jazz record over conventional AM radio, then switched to an FM broadcast. "[I]f the audience of 50 engineers had shut their eyes they would have believed the jazz band was in the same room. There were no extraneous sounds," noted one reporter. He added that several engineers described the invention "as one of the most important radio developments since the first earphone crystal sets were introduced."[13]

In 1937, Armstrong financed construction of the first FM radio station, W2XMN, a 40 kilowatt broadcaster in Alpine, New Jersey. The signal (at 42.8 MHz) could be heard clearly 100 miles (160 km) away, despite the use of less power than an AM radio station.[14]

RCA began to lobby for a change in the law or FCC regulations that would prevent FM radios from becoming dominant. By June 1945, the RCA had pushed the FCC hard on the allocation of electromagnetic frequencies for the fledgling television industry. Although they denied wrongdoing, David Sarnoff and RCA managed to get the FCC to move the FM radio spectrum from (42-50 MHz), to (88-108 MHz), while getting new low-powered community television stations allocated to a new Channel 1 in the 44-50 MHz range. In fairness to the FCC, the 42-50 MHz band was plagued by frequent tropospheric and E-layer stratospheric propagation which caused distant high powered stations to interfere with each other. The problem becomes even more severe on a cyclical basis when sunspot levels reach a maximum every 11 years and lower VHF band signals below 50 MHz can travel across the Atlantic Ocean or from coast to coast within North America on occasion. Sunspot levels were near their cyclical peak when the FCC reallocated FM in 1945. The 88-108 MHz range is a technically better location for FM broadcast because it is less susceptible to this kind of frequent interference. (Channel 1 eventually had to be deleted as well, with all TV broadcasts licensed at frequencies 54 MHz or higher, and the band is no longer widely used for emergency first responders either, those services having moved mostly to UHF.)

But the immediate economic impact of the shift, whatever its technical merit, was devastating to early FM broadcasters. This single FCC action would render all Armstrong-era FM receivers useless within a short time as stations were moved to the new band, while it also protected both RCA's AM-radio stronghold and that of the other major competing networks, CBS, ABC and Mutual. Armstrong's radio network did not survive the shift into the high frequencies and was set back by the FCC decision. This change was strongly supported by AT&T, because loss of FM relaying stations forced radio stations to buy wired links from AT&T.

Furthermore, RCA also claimed invention of FM radio and won its own patent on the technology. A patent fight between RCA and Armstrong ensued. RCA's momentous victory in the courts left Armstrong unable to claim royalties on any FM receivers, including televisions, which were sold in the United States. The undermining of the Yankee Network and his costly legal battles brought ruin to Armstrong, by then almost penniless and emotionally distraught. Eventually, after Armstrong's death, many of the lawsuits were decided or settled in his favor, greatly enriching his estate and heirs. But the decisions came too late for Armstrong himself to enjoy his legal vindication.

Personal life

Armstrong married Sarnoff's secretary, Marion MacInnis, in December 1922. He gave Marion the world's first portable radio as a wedding gift. Armstrong bought a Hispano-Suiza motor car before the wedding, which they drove to Palm Beach, Florida for their honeymoon. He kept the car until his death. He was an avid tennis player until an injury in 1940, and drank an Old Fashioned with dinner.[4]


Financially broken and mentally beaten after years of legal tussles with RCA and others, Armstrong lashed out at his wife one day with a fireplace poker, striking her on the arm. Fearing for her life, Marion Armstrong fled their apartment and went to stay with her sister. Alone and depressed over the FM patent disputes, Armstrong removed the air conditioner from the window, dressed in his coat and hat, and jumped to his death from the thirteenth floor of his New York City apartment on January 31, 1954. His body was found the next morning by a maintenance worker. His suicide note to his wife read: "May God help you and have mercy on my soul".[15][16] Upon hearing the news, David Sarnoff remarked "I did not kill Armstrong." Armstrong's widow Marion renewed the patent fight against RCA and finally prevailed. Unlike her husband, Marion was willing to compromise.[17][18]

Edwin Armstrong was buried in Locus Grove Cemetery, Merrimac, Massachusetts.


It took decades following Armstrong's death for FM broadcasting to meet and surpass the saturation of the AM band, and longer still for FM radio to become profitable for broadcasters. Two developments made a difference in the 1960s. One was the development of true stereophonic broadcasting on FM by General Electric, which resulted in the approval of an FM stereo broadcast standard by the FCC in 1961, and the conversion of hundreds of stations to stereo within a few years.

The other was an FCC rulemaking in 1966 that required broadcasters who owned both fulltime AM stations and FM properties in the same city to program each of them with separate programming during a majority of the day. This meant FM no longer just simulcast AM with better sound quality, but offered unique program choices expanding what listeners could hear. Programmers took advantage by turning their FM stations into venues for formats from country to progressive rock to jazz and classical music, all with the enhanced quality that stereo sound could bring. For example, some AM stations paused Sunday morning music programming for religious voicetracks by ministers. Sister stations on FM continued the music programming.

Within a few years a majority of households were FM equipped, by the 1980s a majority of cars sold had FM stereo radios and a majority of listening in the U.S. was devoted to FM signals according to the Arbitron rating service. The stereo sound revolution, followed by the programming revolution, accomplished what cleaner and crisper sound alone was unable to achieve, and made FM radio a permanent and important part of the communications landscape.

Armstrong was of the opinion that anyone who had actual contact with the development of radio understood that the radio art was the product of experiment and work based on physical reasoning, rather than on the mathematicians' calculations and formulae (known today as part of "mathematical physics"). His work, as important as it was in its own right, was a part of a continuum of progress in communications and electronics that since his time has brought forward color television, the personal computer, the Internet, cable and satellite radio and TV, personal mobile phones, audio, video and computing, digital stereo radio on both the medium wave and VHF-FM bands, and digital high definition television on VHF, UHF, cable and satellite. Armstrong's FM system was used for communications between NASA and the Apollo program astronauts.


Armstrong's house, circa 1975. It was demolished in 1983 due to fire damage.

In 1917 Armstrong was the first recipient of the IRE's, now IEEE Medal of Honor.[19] For his wartime work on radio the French government gave him the Legion of Honor in 1919. He was awarded the 1941 Franklin Medal. He received in 1942 the AIEEs Edison Medal "for distinguished contributions to the art of electric communication, notably the regenerative circuit, the superheterodyne, and frequency modulation". The ITU added him to its roster of great inventors of electricity in 1955. In 1980 he was inducted into the National Inventors Hall of Fame, and was on a U.S. postage stamp in 1983. The Consumer Electronics Hall of Fame inducted him in 2000, "in recognition of his contributions and pioneering spirit that have laid the foundation for consumer electronics."

Philosophy Hall, the Columbia building where Armstrong developed FM, was declared a National Historic Landmark in 2003 in recognition of that fact. Armstrong's home in Yonkers also received designation in both the NHL and the National Register of Historic Places, but both were withdrawn when the house was later demolished.[20][21]

Armstrong Hall at Columbia is also named in his honor. The building, at the northeast corner of Broadway and 112th Street, was originally an apartment house but was converted to research space after Columbia bought it. It is now home to the Goddard Institute for Space Studies, a research institute jointly operated by Columbia and the National Aeronautics and Space Administration dedicated to atmospheric and climate science. A storefront in the corner of the building houses Tom's Restaurant, a longtime neighborhood fixture that was featured as the fictional diner "Monk's" for establishing shots in the television series "Seinfeld". The same restaurant also inspired Susanne Vega's song "Tom's Diner".

In addition, Columbia established the Edwin Howard Armstrong Professorship in Computer Science in Armstrong's memory.

Also, the United States Army Communications and Electronics Life Cycle Management Command (CECOM-LCMC) Headquarters at Aberdeen Proving Ground, Maryland is named Armstrong Hall in his honor.


Armstrong received 42 patents in total; a selection are listed below:

See also

References and notes

  1. ^ a b Tsividis, Yannis (Spring, 2002). "Edwin Armstrong: Pioneer of the Airwaves". Columbia Alumni Magazine. http://www.columbia.edu/cu/alumni/Magazine/Spring2002/Armstrong.html. Retrieved 12 December 2010. 
  2. ^ "The Armstrong Patent". Radio Broadcast (Doubleday, Page, & Co.) 1 (1): 71–72. May 1922. http://books.google.com/books?id=VMcnAAAAYAAJ&pg=PA71. 
  3. ^ There was a dispute regarding who invented superheterodyne radio. For example, Walter Schottky claimed that he had independently invented super heterodyne radio too.
  4. ^ a b c d Lawrence Lessing (1956). Man Of High Fidelity. J. B. Lippincott. 
  5. ^ E. H. Armstrong (1917-08-02). "Operating Features of the Audion". Annals of the New York Academy of Sciences 27 (1): 215–243. doi:10.1111/j.1749-6632.1916.tb55188.x. http://www3.interscience.wiley.com/journal/119811389/abstract?CRETRY=1&SRETRY=0. 
  6. ^ Tom Lewis (1991). Empire of the air: the men who made radio. E. Burlingame Books. ISBN 0060981199. 
  7. ^ Dana M. Raymond: Air War: Legal Battles Over FM Radio
  8. ^ J.R. Carson, Notes on the theory of modulation, Proc. IRE, vol. 10, no. 1 (February 1922),pp. 57-64
  9. ^ E.H. Armstrong, A method of reducing disturbances in radio signaling by a system of frequency modulation, Proc. IRE, vol. 24, no. 5 (May 1936),pp. 689-740.
  10. ^ E.H. Armstrong, A method of reducing disturbances in radio signaling by a system of frequency modulation, Proc. IEEE, vol. 72, no. 8 (August 1984),pp. 1042-1062.
  11. ^ M.G. Crosby, Frequency modulation noise characteristics, Proc. IRE, vol. 25, no. 4 (April 1937), pp. 472-514.
  12. ^ http://users.erols.com/oldradio/eha65.htm
  13. ^ United Press report, "Radio Set-up Eliminates All Noise," Ogden Standard-Examiner, June 18, 1936, p1
  14. ^ Current Biography 1940, pp.23-26.
  15. ^ "Edwin H. Armstrong, Inventor, Dies in Plunge". The Hartford Courant. February 2, 1954. http://pqasb.pqarchiver.com/courant/access/887794342.html?dids=887794342:887794342&FMT=CITE&FMTS=CITE:AI&date=Feb+02%2C+1954&author=&pub=The+Hartford+Courant&desc=Edwin+H.+Armstrong%2C+Inventor%2C+Dies+in+Plunge&pqatl=google. Retrieved 2008-11-21. 
  16. ^ "Died". Time (magazine). February 8, 1954. http://www.time.com/time/magazine/article/0,9171,860424,00.html. Retrieved 2008-06-21. "Edwin Howard Armstrong, 63, electronics genius, one of the fathers of modern radio; by his own hand (a jump from his 13th floor apartment) after writing a note to his wife that concluded: "May God help you and have mercy on my soul"; in Manhattan. In 1913 he worked out the regenerative circuit, which outmoded crystal receiving sets with a sensitive vacuum tube system; his superheterodyne circuit, developed in 1918 while serving in France, is still the basic circuit of AM radio. In 1939, he perfected a method for eliminating static (now known as FM). A professor of electrical engineering at Columbia University for the last 20 years, the earnest, driving inventor earned millions of dollars in patent royalties, died a rich man." 
  17. ^ "Esther Armstrong, 81, the Wife Of Inventor of FM Radio System". New York Times. 1979-08-10, Friday. "Esther Marion Armstrong, the wife of the late Maj. Edwin Howard Armstrong, a leading American inventor, died Wednesday at the Exeter (N.H.) Hospital, after a brief illness. She was 81 years old and lived in Rye Beach, N.H." 
  18. ^ "Armstrong Suit Over FM Settled. R.C.A. and N.B.C. to Pay '$1,000,000' Ending Action Begun by Late Inventor.". New York Times. December 31, 1954. http://select.nytimes.com/gst/abstract.html?res=F40E1EFC345A157B93C3AA1789D95F408585F9. Retrieved 2007-07-21. "The Radio Corporation of America and the National Broadcasting Company have settled for "approximately $1,000,000" claims against them by the estate of the late Maj. Edwin H. Armstrong." 
  19. ^ "IEEE Medal of Honor". IEEE Global History Network. IEEE. 27 June 2011. http://www.ieeeghn.org/wiki/index.php/IEEE_Medal_of_Honor. Retrieved 7 July 2011. 
  20. ^ Sheire, James (July, 1975). "National Register of Historic Places Inventory/Nomination: Edwin H. Armstrong House". http://www.oprhp.state.ny.us/hpimaging/hp_view.asp?GroupView=10774. Retrieved 2008-01-25.  (includes 1 photo)
  21. ^ "Withdrawal of National Historic Landmark Designation: Edwin H. Armstrong House". National Historic Landmark summary listing. National Park Service. http://www.nps.gov/nhl/DOE_dedesignations/Armstrong.htm. Retrieved 2008-01-25. 

Further reading

  • Ira Brodsky. The History of Wireless: How Creative Minds Produced Technology for the Masses. St. Louis: Telescope Books, 2008.
  • Ken Burns. Empire of the Air. Documentary that first aired on PBS in 1992.
  • Gary L. Frost. Early FM Radio: Incremental Technology in Twentieth-Century America. Baltimore: Johns Hopkins University Press, 2010. ISBN 0801894409, ISBN 978-0801894404.
  • Lawrence Lessing. Man of High Fidelity: Edwin Howard Armstrong. Philadelphia: J.B. Lippincott Company, 1956.
  • Tom Lewis. Empire of the Air: the Men Who Made Radio. New York: HarperCollins, 1991.
  • Süsskind, Charles (1970). "Armstrong, Edwin Howard". Dictionary of Scientific Biography. New York: Charles Scribner's Sons. pp. 287–288. ISBN 0684101149. 

External links

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