View source for Edwin Howard Armstrong

{{Short description|American radio-frequency engineer and inventor (1890–1954)}}
{{Use mdy dates|date=December 2024}}
{{Infobox scientist
| name                = Edwin Armstrong
| image               = EdwinHowardArmstrong.jpg
| caption             = Sketch of Armstrong, {{Circa|1954}}
| birth_date          = {{Birth date|1890|12|18}}
| birth_place         = [[New York City]], US<ref name="Columbia">{{cite journal |url=http://www.columbia.edu/cu/alumni/Magazine/Spring2002/Armstrong.html |title=Edwin Armstrong: Pioneer of the Airwaves |author=Tsividis, Yannis |date=Spring 2002 |journal=Columbia Magazine |publisher=Columbia University |location=New York |series=Living Legacies: Great Moments and Leading Figures in the History of Columbia University |access-date=September 18, 2017}}</ref>
| death_date          = {{Death date and age|1954|02|01|1890|12|18}}
| death_place         = New York City, US
| alma_mater          = [[Columbia University]]
| known_for           = {{Plain list|
* [[Armstrong oscillator]]
* [[Armstrong phase modulator]]
* [[Superheterodyne receiver]]
* [[Regenerative circuit]]
* [[FM radio]]}}
| spouse              = {{Marriage|[[Esther Marion Armstrong|Esther Marion McInnis]]|1922}}
| awards              = {{Plain list|
* [[IRE Medal of Honor]] (1917)
* [[Holley Medal]] (1940)
* [[Franklin Medal]] (1941)
* [[AIEE Edison Medal]] (1942)
* [[Washington Award]] (1951)}}
| fields              = [[Radio-frequency engineering]]
| work_institutions   = Columbia University
| academic_advisors   = [[Michael Pupin]]
{{Infobox military person
| embed               = yes
| allegiance          = {{Flagu|United States|1912}}
| branch              = [[United States Army]] 
| branch_label        = Branch
| service_years       = 1917–1919
| rank                = [[Major (United States)|Major]]
| unit                = [[US Army Signal Corps]]
| battles             = [[World War I]]
| battles_label       = Wars
| awards              = [[Legion of Honour]] (1919)
}}
}}

'''Edwin Howard Armstrong''' (December 18, 1890<ref>{{cite web |title=Edwin H. Armstrong |url=https://www.britannica.com/biography/Edwin-H-Armstrong|author=Lawrence P. Lessing|website=Britannica |access-date=December 17, 2018}}</ref> – February 1, 1954<ref name="nyt19540202" />) was an American [[radio-frequency engineer]] and inventor who developed FM ([[frequency modulation]]) radio and the [[superheterodyne]] receiver system.

He held 42 patents and received numerous awards, including the first Medal of Honor awarded by the Institute of Radio Engineers (now [[IEEE]]), the French [[Legion of Honor]], the 1941 [[Franklin Medal]] and the 1942 [[Edison Medal]]. He achieved the rank of major in the [[Signal Corps (United States Army)|U.S. Army Signal Corps]] during [[World War I]] and was often referred to as "Major Armstrong" during his career.<ref name="auto"/>   He was inducted into the [[National Inventors Hall of Fame]] and included in the [[International Telecommunication Union]]'s roster of great inventors. He was inducted into the Wireless Hall of Fame posthumously in 2001.<ref>{{Cite web |title=Edwin Armstrong |url=https://wirelesshistoryfoundation.org/edwin-armstrong/ |url-status=live |archive-url=https://web.archive.org/web/20240315154759/https://wirelesshistoryfoundation.org/edwin-armstrong/ |archive-date=March 15, 2024 |access-date=July 27, 2024 |website=wirelesshistoryfoundation.org|date=April 25, 1999 }}</ref> Armstrong attended Columbia University, and served as a professor there for most of his life. 

Armstrong is also noted for his legal battles with [[Lee de Forest]] and [[David Sarnoff]], two other key figures in developing the early radio industry in the United States. The prolonged litigation took a toll on Armstrong's health and finances, which led to a breakdown in his marriage, followed by his suicide in 1954. Thereafter, his estate's legal cases were pursued by his widow, Marion, who won several successful suits and settlements.

== Early life ==
[[File:EdwinHArmstrongHouse c1975.jpg|right|thumb|Armstrong's boyhood home, overlooking the Hudson River in Yonkers, New York, c. 1975]]

Edwin Howard Armstrong was born on December 18, 1890, in [[Chelsea, Manhattan|Chelsea]], [[New York City]], the eldest of three children of John Armstrong and Emily Smith.<ref name="Columbia"/> His father began working at a young age at the American branch of the [[Oxford University Press]], which published bibles and standard classical works, eventually advancing to the position of vice president.<ref name="nyt19540202" /> His parents first met at the North Presbyterian Church, located at 31st Street and Ninth Avenue. His mother's family had strong ties to Chelsea, and an active role in church functions.<ref>''Man of High Fidelity'' by Lawrence Lessing (1956) [https://archive.org/details/in.ernet.dli.2015.189098/page/n21/mode/1up p. 22]</ref> When the church moved north, the Smiths and Armstrongs followed, and in 1895 the Armstrong family moved from their brownstone row house at 347 West 29th Street to a similar house at 26 West 97th Street on the [[Upper West Side]].<ref>Lessing 1956, [https://archive.org/details/in.ernet.dli.2015.189098/page/n22/mode/1up p. 23]</ref> The family was comfortably middle class.

At the age of eight, Armstrong contracted [[Sydenham's chorea]] (then known as [[Sydenham's chorea|St. Vitus' Dance]]), an infrequent but serious neurological disorder precipitated by rheumatic fever. For the rest of his life, Armstrong was afflicted with a physical [[tic]] exacerbated by excitement or stress. Due to this illness, he withdrew from public school and was home-tutored for two years.<ref>Lessing 1956, [https://archive.org/details/in.ernet.dli.2015.189098/page/n25/mode/1up p. 26]</ref> To improve his health, the Armstrong family moved to a house overlooking the Hudson River, at 1032 Warburton Avenue in [[Yonkers, New York|Yonkers]]. The Smith family subsequently moved next door.<ref>Lessing 1956, [https://archive.org/details/in.ernet.dli.2015.189098/page/n23/mode/1up p. 24]</ref> Armstrong's tic and the time missed from school led him to become socially withdrawn.

From an early age, Armstrong showed an interest in electrical and mechanical devices, particularly trains.<ref name="Lessing-320">Lessing 1956, [https://archive.org/details/in.ernet.dli.2015.189098/page/n26/mode/1up p. 27]</ref> 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. Much of his early research was conducted in the attic of his parents' house.<ref name="Wu-126">{{harvnb|Wu|2010|p=126}}</ref>

In 1909, Armstrong enrolled at Columbia University in New York City, where he became a member of the Epsilon Chapter of the [[Theta Xi]] engineering fraternity, and studied under Professor [[Mihajlo Pupin|Michael Pupin]] at the Hartley Laboratories, a separate research unit at Columbia. Another of his instructors, Professor John H. Morecroft, later remembered Armstrong as being intensely focused on the topics that interested him, but somewhat indifferent to the rest of his studies.<ref>[https://babel.hathitrust.org/cgi/pt?id=iau.31858044013914&view=1up&seq=274 "What Everyone Should Know About Radio History: Part II"] by Prof. J. H. Morecroft, ''Radio Broadcast'', August 1922, pp. 294–302.</ref> Armstrong challenged conventional wisdom and was quick to question the opinions of both professors and peers. In one case, he recounted how he tricked a visiting professor from [[Cornell University]] that he disliked into receiving a severe electrical shock.<ref>''Empire of the Air'' by Tom Lewis, 1991, pp. 60–61.</ref> He also stressed the practical over the theoretical, stating that progress was more likely the product of experimentation and reasoning than on mathematical calculation and the formulae of "[[mathematical physics]]."

Armstrong graduated from Columbia in 1913, earning an electrical engineering degree.<ref name="auto">{{cite book|title=Who Was Who in American History – the Military|date=1975|publisher=Marquis Who's Who|location=Chicago|isbn=0837932017|page=15}}</ref>

During [[World War I]], Armstrong served in the [[Signal Corps (United States Army)|Signal Corps]] as a captain and later a major.<ref name="auto"/>

Following college graduation, he received a $600 one-year appointment as a laboratory assistant at Columbia, after which he nominally worked as a research assistant, for a salary of $1 a year, under Professor Pupin.<ref>''The Legacies of Edwin Howard Armstrong'', "E. H. Armstrong" by Thomas Sykes, 1990, p. 22.</ref> Unlike most engineers, Armstrong never became a corporate employee. He set up a self-financed independent research and development laboratory at Columbia, and owned his patents outright.

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.<ref name="nyt19340807">{{cite news |title=Major Armstrong Goes to Columbia |newspaper=The New York Times |issn=0362-4331 |date=August 7, 1934 |page=20 |quote=The appointment of Major Edwin Howard Armstrong as Professor of Electrical Engineering at Columbia University yesterday by Dr. Nicholas Murray Butler, president of the university.}}</ref>

== Early work ==
=== Regenerative circuit ===
[[File:Armstrong circuit.png|right|thumb|350px|Armstrong's "feed back" circuit drawing, from ''Radio Broadcast'' vol. 1 no. 1 1922.]]

Armstrong began working on his first major invention while still an undergraduate at Columbia. In late 1906, [[Lee de Forest]] had invented the three-element (triode) [[audion|"grid Audion"]] vacuum-tube. How vacuum tubes worked was not understood at the time. De Forest's initial Audions did not have a high vacuum and developed a blue glow at modest plate voltages; De Forest improved the vacuum for Federal Telegraph.<ref>''DeForest Radio Co. v. General Electric Co.'', [https://law.resource.org/pub/us/case/reporter/US/283/283.US.664.630.html 283 U.S. 664] (May 25, 1931). Fleming and Lilenfeld had advocated high vacuum. "Of critical importance in the present controversy is the effect of the presence of gas within the tube."  "In consequence, the low vacuum tube is more sensitive both as a detector and as an amplifier than a tube of high vacuum." "August 20, 1912, the earliest date claimed for Langmuir, was rejected rightly, we think, by the District Court, which held that Langmuir was anticipated by Arnold in November, 1912. But before the earlier date, De Forest sought and obtained a high vacuum in the audions used as amplifiers, and observed that when the vacuum was too low the blue glow effect occurred at from 15 to 20 volts. To secure higher voltages from the audions used as amplifiers and to procure the requisite high vacuum, he had some of the bulbs re-exhausted while superheated. By August 1912, the Telegraph Company used De Forest amplifying audions at 54 volts, and by November, they were used by another at 67.5 volts. This was possible only because the tubes had been exhausted of gas, which would otherwise have ionized with blue glow at from 20 to 30 volts."</ref> By 1912, vacuum tube operation was understood, and regenerative circuits using high-vacuum tubes were appreciated.

While growing up, Armstrong had experimented with the early temperamental, "gassy" Audions. Spurred by the later discoveries, he developed a keen interest in gaining a detailed scientific understanding of how vacuum tubes worked. In conjunction with Professor Morecroft he used an [[oscillograph]] to conduct comprehensive studies.<ref>[https://babel.hathitrust.org/cgi/pt?id=uva.x002212112&view=1up&seq=1175 "Operating Features of the Audion"] by E. H. Armstrong, ''Electrical World'', December 12, 1914, pages 1149-1152.</ref> His breakthrough discovery was determining that employing [[Positive feedback#In electronics|positive feedback]] (also known as [[Regenerative circuit|"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. Further investigation revealed that when the feedback was increased beyond a certain level a vacuum-tube would go into [[Electronic oscillator|oscillation]], thus could also be used as a continuous-wave radio transmitter.

Beginning in 1913 Armstrong prepared a series of comprehensive demonstrations and papers that carefully documented his research,<ref name="Armstrong-audion">{{cite journal |doi = 10.1111/j.1749-6632.1916.tb55188.x |url=https://babel.hathitrust.org/cgi/pt?id=hvd.hwsqz1&view=1up&seq=275 |first=E. H. |last=Armstrong |author-link=Edwin Howard Armstrong |title=Operating Features of the Audion |journal=Annals of the New York Academy of Sciences |volume=27 |issue=1 |pages=215–243 |date=August 2, 1917|s2cid = 85101768}}</ref> and in late 1913 applied for patent protection covering the regenerative circuit. On October 6, 1914, {{US patent|1,113,149}} was issued for his discovery.<ref>Lewis (1991), pages 77, 87.</ref> Although Lee de Forest initially discounted Armstrong's findings, beginning in 1915 de Forest filed a series of competing patent applications that largely copied Armstrong's claims, now stating that he had discovered regeneration first, based on a notebook entry made on August 6, 1912, while working for the Federal Telegraph company, prior to the date recognized for Armstrong of January 31, 1913. The result was an interference hearing at the patent office to determine priority. De Forest was not the only other inventor involved – the four competing claimants included Armstrong, de Forest, General Electric's [[Irving Langmuir|Langmuir]], and [[Alexander Meissner]], who was a German national, which led to his application being seized by the [[Office of Alien Property Custodian]] during World War I.<ref>''Ibid.'', page 192.</ref>

Following the end of WWI Armstrong enlisted representation by the law firm of Pennie, Davis, Martin and Edmonds. To finance his legal expenses he began issuing non-transferable licenses for use of the regenerative patents to a select group of small radio equipment firms, and by November 1920, 17 companies had been licensed.<ref>''Invention and Innovation in the Radio Industry'' by W. Rupert Maclaurin, 1949, page 122.</ref> These licensees paid 5% royalties on their sales which were restricted to only "amateurs and experimenters". Meanwhile, Armstrong explored his options for selling the commercial rights to his work. Although the obvious candidate was the [[Radio Corporation of America]] (RCA), on October 5, 1920, the [[Westinghouse Electric & Manufacturing Company]] took out an option for $335,000 for the commercial rights for both the regenerative and superheterodyne patents, with an additional $200,000 to be paid if Armstrong prevailed in the regenerative patent dispute. Westinghouse exercised this option on November 4, 1920.<ref>''Radio Manufacturers of the 1920s: Volume 3'' by Alan Douglas, 1991, page 3. Organized broadcasting barely existed when the initial amateur and experimental licenses were granted. By 1922 a broadcast boom in the US saw tremendous growth in the sale of radio receivers to the general public. Westinghouse tried to claim that these sales infringed on its rights, as they should be considered "commercial", but the courts disagreed. Thus, the companies that held these "amateur and experimental" license rights found they now had a valuable asset.</ref>

Legal proceedings related to the regeneration patent became separated into two groups of court cases. An initial court action was triggered in 1919 when Armstrong sued de Forest's company in district court, alleging infringement of patent 1,113,149. This court ruled in Armstrong's favor on May 17, 1921. A second line of court cases, the result of the patent office interference hearing, had a different outcome. The interference board had also sided with Armstrong, but he was unwilling to settle with de Forest for less than what he considered full compensation. Thus pressured, de Forest continued his legal defense, and appealed the interference board decision to the District of Columbia district court. On May 8, 1924, that court ruled that it was de Forest who should be considered regeneration's inventor. Armstrong (along with much of the engineering community) was shocked by these events, and his side appealed this decision. Although the legal proceeding twice went before the US Supreme Court, in 1928 and 1934, he was unsuccessful in overturning the decision.<ref>Douglas (1991), pages 193-198, 203.</ref>

In response to the second Supreme Court decision upholding de Forest as the inventor of regeneration, Armstrong attempted to return his 1917 [[Institute of Radio Engineers|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". The organization's board refused to allow him, and issued a statement that it "strongly affirms the original award".

=== Superheterodyne circuit ===
[[File:Edwin H Armstrong in WWI 1922.png|thumb|right|Armstrong in his Signal Corps uniform during [[World War I]]]]

The United States entered WWI in April 1917. Later that year, Armstrong was commissioned as a captain in the [[Signal Corps (United States Army)|U.S. Army Signal Corps]], and assigned to a laboratory in Paris, France to help develop radio communication for the Allied war effort. He returned to the US in the autumn of 1919, after being promoted to the rank of Major.<ref name="Lessing-320" /> (During both world wars, Armstrong gave the US military free use of his patents.)

During this period, Armstrong's most significant accomplishment was the development of a "supersonic heterodyne" – soon shortened to "superheterodyne" – radio receiver circuit.<ref name="nyt19540202" /> This circuit made radio receivers more sensitive and selective and is used extensively today. The key feature of the superheterodyne approach is the mixing of the incoming radio signal with a locally generated, different frequency signal within a radio set. That circuit is called the mixer. The result is a fixed, unchanging intermediate frequency, or I.F. signal which is easily amplified and detected by following circuit stages. In 1919, Armstrong filed an application for a US patent of the superheterodyne circuit which was issued the next year. This patent was subsequently sold to Westinghouse.<ref>MacLaurin (1949), page 106. "Westinghouse then made an even more important move by purchasing [on May 22, 1920] for $335,000 the Armstrong patents on the regenerative and superheterodyne circuits."</ref> The patent was challenged, triggering another patent office interference hearing.<ref name="who">[http://antiqueradios.com/superhet/ "Who Invented the Superheterodyne?"] {{Webarchive|url=https://web.archive.org/web/20111011084603/http://www.antiqueradios.com/superhet/ |date=October 11, 2011 }} by Alan Douglas, originally published in ''The Legacies of Edwin Howard Armstrong'' from the "Proceedings of the Radio Club of America", Nov. 1990, Vol.64 no.3, pages 123-142. Page 139: "Lévy broadened his claims to purposely create an interference, by copying Armstrong's claims exactly. The Patent Office would then have to choose between the two inventors."</ref> Armstrong ultimately lost this patent battle; although the outcome was less controversial than that involving the regeneration proceedings.<ref>Lewis (1991), page 205. "...the case did not seem to affect Armstrong emotionally in the same way the regeneration suit did... Possibly he recognized the Frenchman did have some legitimate claim to the invention... Armstrong respected Levy in a way that he could not respect de Forest..."</ref>

The challenger was [[Lucien Lévy]] of France who had worked developing Allied radio communication during WWI. He had been awarded French patents in 1917 and 1918 that covered some of the same basic ideas used in Armstrong's superheterodyne receiver. 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. The subsequent court reviews continued until 1928, when the District of Columbia Court of Appeals disallowed all nine claims of Armstrong's patent, assigning priority for seven of the claims to Lévy, and one each to [[Ernst Alexanderson]] of General Electric and Burton W. Kendall of [[Bell Laboratories]].<ref>''The Continuous Wave: Technology and American Radio, 1900-1932'' by Hugh G. J. Aitken, 1985, page 467.</ref>

Although most early radio receivers used regeneration Armstrong approached RCA's [[David Sarnoff]], whom he had known since giving a demonstration of his regeneration receiver in 1913, about the corporation offering superheterodynes as a superior offering to the general public.<ref>''History of Radio to 1926'' by Gleason L. Archer, 1938, [https://babel.hathitrust.org/cgi/pt?id=wu.89074767138&view=1up&seq=343 page 297]: "It appears that Armstrong first exhibited the device to the astute General Manager of RCA, David Sarnoff. Mr. Sarnoff had just concluded arrangements that involved ordering several millions' dollars worth of an improved type of radio... He was so impressed by the Armstrong invention that he at once halted these negotiations..."</ref> (The ongoing patent dispute was not a hindrance, because extensive cross-licensing agreements signed in 1920 and 1921 between RCA, Westinghouse and AT&T meant that Armstrong could freely use the Lévy patent.) Superheterodyne sets were initially thought to be prohibitively complicated and expensive as the initial designs required multiple tuning knobs and used nine vacuum tubes. In conjunction with RCA engineers, Armstrong developed a simpler, less costly design. RCA introduced its superheterodyne Radiola sets in the US market in early 1924, and they were an immediate success, dramatically increasing the corporation's profits. These sets were considered so valuable that RCA would not license the superheterodyne to other US companies until 1930.<ref name="who"/>

=== Super-regeneration circuit ===
[[Image:Edwin Armstrong at blackboard.jpg|thumb|Armstrong explaining the superregenerative circuit, New York, 1922]]

The regeneration legal battle had one serendipitous outcome for Armstrong. 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. A year later, in 1922, Armstrong sold his super-regeneration patent to RCA for $200,000 plus 60,000 shares of corporation stock, which was later increased to 80,000 shares in payment for consulting services. This made Armstrong RCA's largest shareholder, and he noted that "The sale of that invention was to net me more than the sale of the regenerative circuit and the superheterodyne combined".<ref>Maclaurin (1949). October 12, 1947, letter from Armstrong to the author, page 122.</ref> RCA envisioned selling a line of super-regenerative receivers until superheterodyne sets could be perfected for general sales, but it turned out the circuit was not selective enough to make it practical for broadcast receivers.

==Wide-band FM radio==

"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. Many ideas for static elimination were investigated, with little success. In the mid-1920s, Armstrong began researching a solution. He initially, and unsuccessfully, attempted to resolve the problem by modifying the characteristics of AM transmissions.

One approach used frequency modulation (FM) transmissions. Instead of varying the strength of the carrier wave as with AM, the frequency of the carrier was changed to represent the audio signal. 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.<ref>{{citation |first=J. R. |last=Carson |author-link=John Renshaw Carson |url=https://babel.hathitrust.org/cgi/pt?id=chi.101888973&view=1up&seq=65 |title=Notes on the theory of modulation |journal=Proceedings of the Institute of Radio Engineers |volume=10 |issue=1 |date=February 1922 |pages=57–64 |doi=10.1109/jrproc.1922.219793 |bibcode=1922PIRE...10...57C }}</ref> Although the [[Carson bandwidth rule]] for FM is important today, Carson's review turned out to be incomplete, as it analyzed only (what is now known as) "narrow-band" FM.

In early 1928 Armstrong began researching the capabilities of FM. Although there were others involved in FM research at this time, he knew of an RCA project to see if FM shortwave transmissions were less susceptible to fading than AM. In 1931 the RCA engineers constructed a successful FM shortwave link transmitting the Schmeling–[[Young Stribling|Stribling]] fight broadcast from California to Hawaii, and noted at the time that the signals seemed to be less affected by static. The project made little further progress.<ref>''Early FM Radio'' by Gary L. Frost, 2010, pages 72-73.</ref>

Working in secret in the basement laboratory of Columbia's [[Philosophy Hall]], Armstrong developed "wide-band" FM, in the process discovering significant advantages over the earlier "narrow-band" FM transmissions. In a [[Frequency modulation#modulation index|"wide-band" FM system]], the deviations of the carrier frequency are made to be much larger than the frequency of the audio signal which can be shown to provide better noise rejection. He was granted five US patents covering the basic features of the new system on December 26, 1933.<ref>{{cite web|url=http://www.fathom.com/seminars/10701020/session2.html |title=Air War: Legal Battles Over FM Radio |first=Dana M |last=Raymond |work=Fathom |publisher=Columbia University |url-status=dead |archive-url=https://web.archive.org/web/20080515054100/http://www.fathom.com/seminars/10701020/session2.html |archive-date=May 15, 2008  }}</ref> Initially, the primary claim was that his FM system was effective at filtering out the noise produced in receivers, by vacuum tubes.<ref>Frost (2010), page 95.</ref>

Armstrong had a standing agreement to give RCA the [[right of first refusal]] to his patents. In 1934 he presented his new system to RCA president Sarnoff. Sarnoff was somewhat taken aback by its complexity, as he had hoped it would be possible to eliminate static merely by adding a simple device to existing receivers. 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. An antenna attached to the building's spire transmitted signals for distances up to {{convert|80|mi|km}}.<ref name="Wu-125">{{harvnb|Wu|2010|p=125}}</ref> These tests helped demonstrate FM's static-reduction and high-fidelity capabilities. RCA, which was heavily invested in perfecting TV broadcasting, chose not to invest in FM, and instructed Armstrong to remove his equipment.<ref>{{cite web |url=http://users.erols.com/oldradio/eha65.htm |title=Beginning of Armstrong's FM station W2XMN at Alpine, NJ (1937) |first=Mike |last=Katzdorn |access-date=December 19, 2011}}</ref>

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 Electronics|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]]. Making existing AM radio transmitters and receivers obsolete would necessitate that stations buy replacement transmitters and listeners purchase FM-capable receivers. In 1936 he published a landmark paper in the ''Proceedings of the IRE'' that documented the superior capabilities of using wide-band FM.<ref>{{citation|first=E. H. |last=Armstrong |author-link=Edwin Howard Armstrong |title=A method of reducing disturbances in radio signaling by a system of frequency modulation |journal=Proc. IRE |volume=24 |issue=5 |date=May 1936 |pages=689–740 |doi=10.1109/jrproc.1936.227383 |bibcode=1936PIRE...24..689A |s2cid=43628076 }}</ref> (This paper would be reprinted in the August 1984 issue of ''[[Proceedings of the IEEE]]''.)<ref>{{citation|first=E. H. |last=Armstrong |author-link=Edwin Howard Armstrong |title=A method of reducing disturbances in radio signaling by a system of frequency modulation |journal=Proc. IEEE |volume=72 |issue=8 |date=August 1984 |pages=1042–1062 |doi=10.1109/proc.1984.12971 |bibcode=1984IEEEP..72.1042A }}</ref> A year later, a paper by Murray G. Crosby (inventor of [[Crosby system]] for FM Stereo) in the same journal<ref>{{citation |first=M. G. |last=Crosby |title=Frequency modulation noise characteristics |journal=Proc. IRE |volume=25 |issue=4 |date=April 1937 |pages=472–514 |doi=10.1109/jrproc.1937.229050|bibcode=1937PIRE...25..472C |s2cid=51643329 }}</ref> provided further analysis of the wide-band FM characteristics, and introduced the concept of "threshold", demonstrating that there is a superior [[signal-to-noise ratio]] when the signal is stronger than a certain level.

In June 1936, Armstrong gave a formal presentation of his new system at the US [[Federal Communications Commission]] (FCC) headquarters. For comparison, he played a jazz record using a conventional AM radio, then switched to an FM transmission. A [[United Press International|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. There were no extraneous sounds." Moreover, "Several engineers said after the demonstration that they consider Dr. Armstrong's invention one of the most important radio developments since the first earphone crystal sets were introduced." 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."<ref>[https://cdnc.ucr.edu/cgi-bin/cdnc?a=d&d=SBS19360618.1.2 "New Static-Less Radio Broadcast Eliminates All Extraneous Noises"] (UP), ''San Bernardino (California) Sun'', June 18, 1936, page 2.</ref>

[[File:Armstrong FM radio station W2XMN Alpine NJ 1940.jpg|thumb|right|250px|Armstrong arranged for the construction of a [[Armstrong Tower|transmission tower in Alpine]], New Jersey, near New York City, and financed demonstration operation of W2XMN, the first FM radio station. W2XMN's antenna is mounted between the top two tiers, visible as a vertical line at the far upper right.<ref>[https://books.google.com/books?id=gycDAAAAMBAJ&pg=PA73 "What are the facts about FM?"] by E. W. Murtfeldt, ''Popular Science'', November 1940, page 73.</ref>]] 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". In 1937 it introduced what became known as the [[Apex (radio band)|Apex band]], consisting of 75 broadcasting frequencies from 41.02 to 43.98&nbsp;MHz. As on the standard broadcast band, these were AM stations but with higher quality audio – in one example, a frequency response from 20&nbsp;Hz to 17,000&nbsp;Hz +/-&nbsp;1&nbsp;dB – because station separations were 40&nbsp;kHz instead of the 10&nbsp;kHz spacings used on the original AM band.<ref>[http://www.theradiohistorian.org/Apex/Apex1.htm America's Apex Broadcasting Stations of the 1930s] by John Schneider.</ref> Armstrong worked to convince the FCC that a band of FM broadcasting stations would be a superior approach. That year he financed the construction of the first FM radio station, [[W2XMN]] (later [[KE2XCC]]) at Alpine, New Jersey. FCC engineers had believed that transmissions using high frequencies would travel little farther than line-of-sight distances, limited by the horizon. When operating with 40 kilowatts on 42.8&nbsp;MHz, the station could be clearly heard {{convert|100|mi|km}} away, matching the daytime coverage of a full power 50-kilowatt AM station.<ref>{{cite journal|year=1940 |title=Armstrong, Edwin Howard |journal=Current Biography |pages=23–26 |publisher=The H. W. Wilson Company}}</ref>

FCC studies comparing the Apex station transmissions with Armstrong's FM system concluded that his approach was superior. In early 1940, the FCC held hearings on whether to establish a commercial FM service. Following this review, the FCC announced the establishment of an FM band effective January 1, 1941, consisting of forty 200&nbsp;kHz-wide channels on a band from 42 to 50&nbsp;MHz, with the first five channels reserved for educational stations.<ref>[https://babel.hathitrust.org/cgi/pt?id=uiug.30112059131711&view=1up&seq=767 "FCC Order No. 67"], ''Federal Register'', May 25, 1940, page 2011.</ref>   Existing Apex stations were notified that they would not be allowed to operate after January 1, 1941, unless they converted to FM.<ref>[https://babel.hathitrust.org/cgi/pt?id=hvd.32044107899262&view=1up&seq=91 "FCC Order No. 69"] Federal Communications Commission, May 22, 1940.</ref>

Although there was interest in the new FM band by station owners, construction restrictions that went into place during WWII limited the growth of the new service. Following the end of WWII, the FCC moved to standardize its frequency allocations. One area of concern was the effects of [[Tropospheric propagation|tropospheric]] and [[Sporadic E propagation]], which at times reflected station signals over great distances, causing mutual interference. A particularly controversial proposal, spearheaded by RCA, was that the FM band needed to be shifted to higher frequencies to avoid this problem. This reassignment was fiercely opposed as unneeded by Armstrong, but he lost. The FCC made its decision final on June 27, 1945.<ref name=":0">{{Cite news|url=https://www.newspapers.com/image/298622331|title=Device to make FM Radios Work Under FCC Ruling|last=AP|date=June 27, 1945|work=The Miami News|access-date=August 14, 2017|at=6-A|language=en|via=Newspapers.com}}</ref> It allocated 100 FM channels from 88 to 108&nbsp;MHz, and assigned the former FM band to 'non government fixed and mobile' (42–44&nbsp;MHz), and [[Channel 1 (North American TV)|television channel 1]] (44–50&nbsp;MHz), now sidestepping the interference concerns.<ref name=":0" /> A period of allowing existing FM stations to broadcast on both low and high bands ended at midnight on January 8, 1949, at which time any low band transmitters were shut down, making obsolete 395,000<ref>{{Cite news|url=https://www.newspapers.com/image/93688720|title=395,000 FM Radio Sets Must Be Replaced|last=INS|date=June 27, 1945|work=Journal Gazette|access-date=August 14, 2017|page=6|language=en|via=Newspapers.com}}</ref> receivers that had already been purchased by the public for the original band. Although converters allowing low band FM sets to receive high band were manufactured, they ultimately proved to be complicated to install, and often as (or more) expensive than buying a new high band set outright.<ref>{{Cite news|url=https://www.newspapers.com/image/308647368|title=Pre-War FM Radio Sets to Become Obsolete Saturday|date=January 6, 1949|work=The Times|access-date=August 14, 2017|page=1|language=en|via=Newspapers.com}}</ref>

Armstrong felt the FM band reassignment had been inspired primarily by a desire to cause a disruption that would limit FM's ability to challenge the existing radio industry, including RCA's AM radio properties that included the NBC radio network, plus the other major networks including CBS, ABC and Mutual. The change was thought to have been favored by AT&T, as the elimination of FM relaying stations would require radio stations to lease wired links from that company. Particularly galling was the FCC assignment of TV channel 1 to the 44–50&nbsp;MHz segment of the old FM band. Channel 1 was later deleted, since periodic [[radio propagation]] would make local TV signals unviewable.

Although the FM band shift was an economic setback, there was reason for optimism. A book published in 1946 by Charles A. Siepmann heralded FM stations as "Radio's Second Chance".<ref>''Radio's Second Chance'' by Charles A. Siepmann, 1946, pages 239-253.</ref> In late 1945, Armstrong contracted with John Orr Young, founding member of the public relations firm [[Young & Rubicam]], to conduct a national campaign promoting FM broadcasting, especially by educational institutions. Article placements promoting both Armstrong personally and FM were made with general circulation publications including ''[[The Nation]]'', ''[[Fortune (magazine)|Fortune]]'', ''[[The New York Times]]'', ''[[Atlantic Monthly]]'', and ''[[The Saturday Evening Post]]''.<ref>[https://scholarworks.rit.edu/cgi/viewcontent.cgi?article=4076&context=theses "A Case study of Edwin Howard Armstrong's public relations campaign for FM"] (thesis) by Jessica Francis, December 14, 2012, pages 16, 19.</ref>

In 1940, RCA offered Armstrong $1,000,000 for a non-exclusive, royalty-free license to use his FM patents. He refused this offer, because he felt this would be unfair to the other licensed companies, which had to pay 2% royalties on their sales. Over time this impasse with RCA dominated Armstrong's life. RCA countered by conducting its own FM research, eventually developing what it claimed was a non-infringing FM system. The corporation encouraged other companies to stop paying royalties to Armstrong. 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.<ref>Lewis (1991), pages 247-278, 300-328.</ref>

== FM radar ==
During World War II, Armstrong turned his attention to investigations of continuous-wave FM radar funded by government contracts. Armstrong hoped that the interference fighting characteristic of wide-band FM and a narrow receiver bandwidth to reduce noise would increase range. Primary development took place at Armstrong's Alpine, NJ laboratory. A duplicate set of equipment was sent to the U.S. Army's Evans Signal Laboratory. The results of his investigations were inconclusive, the war ended, and the project was dropped by the Army.

Under the name [[Project Diana]], the Evans staff took up the possibility of bouncing radar signals off the moon. Calculations showed that standard pulsed radar like the stock SCR-271 would not do the job; higher average power, much wider transmitter pulses, and very narrow receiver bandwidth would be required. They realized that the Armstrong equipment could be modified to accomplish the task.<ref>{{cite book | first=Cindy Stodola | last=Pomerleau | year=2021 | title=To the Moon and Back: Essays on the Life and Times of Project Diana | pages=91–96 | publisher=Amazon Digital Services LLC - KDP Print US | isbn=979-8-706-54632-8 }}</ref><ref>{{cite web | title=Project Diana: Radar Reaches the Moon | url=https://www.projectdiana-eme.com/| accessdate=July 13, 2022}}</ref> The FM modulator of the transmitter was disabled and the transmitter keyed to produce quarter-second CW pulses. The narrow-band (57&nbsp;Hz) receiver, which tracked the transmitter frequency, got an incremental tuning control to compensate for the possible 300&nbsp;Hz Doppler shift on the lunar echoes. They achieved success on January 10, 1946.

== Death ==
The numerous protracted patent fights caused Armstrong's health to suffer and his behavior grew erratic. On one occasion he came to believe that someone had poisoned his food and insisted on having his stomach pumped. 
According to ''They Made America'' – authored by Sir Harold Evans and others – Armstrong was oblivious to the toll his struggle was taking on Marion. Marion spent months in a mental hospital after she threw herself into the [[East River]].<ref name=TheyMadeAmerica>
{{cite book
| url         = https://books.google.com/books?id=fDyckjF2IWgC&q=marion&pg=PT280
| title       = They Made America: From the Steam Engine to the Search Engine: Two Centuries of Innovators
| publisher   = [[Hachette Digital]]
| author      = Harold Evans | author2=Gail Buckland | author3=[[David Lefer]]
| year        = 2009
| isbn        = 9780316070348
| accessdate  = 2013-08-25
| quote       = The stress of living with a man obsessed put Marion into Psychiatric care. She tried to jump into the East River. She spent months in a mental hospital. Armstrong seemed oblivious to everything except the injustice being done to him.
}}
</ref>

The legal battles also brought Armstrong to the brink of financial ruin. On November 1, 1953, Armstrong told Marion that he had used up almost all his financial resources.<ref name=BioDictRadioArmstrong>
{{cite book 
| url         = https://books.google.com/books?id=mdQq-663faAC&q=%22Marion+McInnis%22+OR+%22Marion+Armstrong%22+radio+OR+FM+OR+RCA&pg=PA12
| title       = Biographical Dictionary of Radio
| publisher   = [[Routledge Publishing]]
| author      = Christopher H. Sterling
| year        = 2013
| page        = 12
| location    = 
| isbn        = 9781136993756
| accessdate  = 2013-08-25
| quote       = The years of litigation had taken their toll. His one-time friend David Sarnoff was now his bitter enemy. His fortune was depleted. In a fit of rage in November 1953, he took his anger out on Marion, his wife of 30 years, and she fled their apartment.
}}
</ref> In better times, funds for their retirement were put in her name, and he asked her to release a portion of those funds so he could continue litigation. She declined, and suggested he consider accepting a settlement. Enraged, Armstrong picked up a fireplace poker, striking her on the arm. Marion left the apartment to stay with her sister and never saw Armstrong again.<ref>{{Citation |last=Stashower |first=Daniel |title=The Boy Genius and the Mogul: the untold story of television |url=https://archive.org/details/boygeniusmogulun00stas |location=New York |publisher=Broadway Books |year=2002 |isbn=0767907590 |quote=His health began to suffer and his behavior grew erratic. On one occasion he came to believe that someone had poisoned his food and insisted on having his stomach pumped. On another, his wife fled the house as Armstrong lashed out with a fireplace poker. }}</ref><ref name="nyt19540202">{{cite news |title=Armstrong, FM Inventor, Dies In Leap From East Side Suite |newspaper=The New York Times |issn=0362-4331 |date=February 2, 1954 |page=1}}</ref><ref name=BioDictRadioArmstrong/>

After just under three months of separation from Marion, sometime during the night of January 31{{snd}}February 1, 1954, Armstrong jumped to his death from a window in his 12-room apartment on the 13th floor of [[River House (New York City)|River House]] in [[Manhattan]], New York City.<ref>[https://archive.org/stream/broadcastingtele46unse#page/n664/mode/1up/ "Maj. Edwin Armstrong, Father of FM, Other Radio Inventions, Dead at 63"], ''Broadcasting-Telecasting'', February 8, 1954, pages 67-68.</ref> 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." The note concluded, "God keep you and Lord have mercy on my Soul."<ref name="nyt19540202" /><ref name="kaempffer">{{cite news |title=Stubborn genius |first=Waldemar |last=Kaempffert |newspaper=The New York Times |date=December 9, 1956 |page=297 |quote = After he penned the last sentence, "God keep you and the Lord have mercy on my soul," he put on his overcoat, hat and gloves and stepped out of a window thirteen stories above the ground.|id={{ProQuest|113472829}} }}</ref> 

[[David Sarnoff]] disclaimed any responsibility, telling [[Carl Dreher]] directly that "I did not kill Armstrong."<ref>Dreher (1976), page 207.</ref> After his death, a friend of Armstrong estimated that 90 percent of his time was spent on litigation against RCA.<ref name="nyt19540202" /> U.S. 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".<ref>[https://archive.org/stream/broadcastingtele46unse#page/n665/mode/1up/ "Major Armstrong Felt Reds Stole His Ideas—McCarthy"], ''Broadcasting-Telecasting'', February 8, 1954, page 68.</ref>

Following her husband's suicide, Marion Armstrong took charge of pursuing his estate's legal cases. In late December 1954, it was announced that through [[arbitration in the United States|arbitration]] a settlement of "approximately $1,000,000" had been made with RCA. Dana Raymond of Cravath, Swaine & Moore in New York served as counsel in that litigation. Marion Armstrong was able to formally establish Armstrong as the inventor of FM following protracted court proceedings over five of his basic FM patents,<ref>{{cite news |title= Fm Suit Settlement Ends Six-Year Fight|magazine=Broadcasting-Telecasting|page=84 |url=https://archive.org/stream/broadcastingtele48unse#page/n195/mode/1up |date=January 10, 1955}}</ref> with a series of successful suits, which lasted until 1967, against other companies that were found guilty of infringement.<ref>Lewis (1991), page 358.</ref>

== Legacy ==
It was not until the 1960s that FM stations in the United States started to challenge the popularity of the AM band, helped by the development of FM stereo by General Electric, followed by the FCC's [[FM Non-Duplication Rule]], which limited large-city broadcasters with AM and FM licenses to simulcasting on those two frequencies for only half of their broadcast hours. Armstrong's FM system was also used for communications between [[NASA]] and the [[Apollo program]] astronauts.

A US Postage Stamp was released in his honor in 1983 in a series commemorating American Inventors.<ref>{{cite web| url = https://postalmuseum.si.edu/object/npm_1999.2004.316.1-4| title = American Inventors, September 21, 1983, Smithsonian Postal Museum}}</ref>

Armstrong has been called "the most prolific and influential inventor in radio history".<ref name="Campbell">{{cite book | last = Campbell | first = Richard |author2=Christopher R. Martin |author3=Bettina Fabos | title = Media and Culture: An Introduction to Mass Communication, 8th Ed. | publisher = MacMillan | year = 2011 | pages = 124 | url = https://books.google.com/books?id=WuqjReIZ4TcC&q=%22edwin+armstrong%22&pg=PA124 | isbn = 978-0312644659}}</ref> The superheterodyne process is still extensively used by radio equipment. Eighty years after its invention, FM technology has started to be supplemented, and in some cases replaced, by more efficient digital technologies. The introduction of digital television eliminated the FM audio channel that had been used by analog television, [[HD Radio]] has added digital sub-channels to FM band stations, and, in Europe and Pacific Asia, [[Digital Audio Broadcasting]] bands have been created that will, in some cases, eliminate existing FM stations altogether.<ref>[https://www.hollywoodreporter.com/news/norway-first-country-end-fm-790131 "Norway to Become First Country to Switch Off FM Radio in 2017"] by Scott Roxborough, ''The Hollywood Reporter'', April 20, 2015.</ref> However, FM broadcasting is still used internationally, and remains the dominant system employed for audio broadcasting services.

== Personal life ==
[[Image:First portable radio, 1923 -b.jpg|thumb|Armstrong and his new wife Esther Marion McInnis in Palm Beach in 1923. The radio is a portable superheterodyne that Armstrong built as a present for her.]]

In 1923, combining his love for high places with courtship rituals, Armstrong climbed the [[WABC (AM)|WJZ]] (now WABC) antenna located atop a 20-story building in New York City, where he reportedly did a handstand, and when a witness asked him what motivated him to "do these damnfool things", Armstrong replied "I do it because the spirit moves me."<ref>Dreher (1976), page 46.</ref> Armstrong had arranged to have photographs taken, which he had delivered to David Sarnoff's secretary, Marion McInnis.<ref>Lewis (1991), page 160. Three of the photographs are included in the pictorial section between pages 118-119.</ref> Armstrong and McInnis married later that year.<ref name="Wu-126" /> Armstrong bought a [[Hispano-Suiza]] motor car before the wedding, which he kept until his death, and which he drove to Palm Beach, Florida for their honeymoon. A publicity photograph was made of him presenting Marion with the world's first portable superheterodyne radio as a wedding gift.<ref name="Lessing-320" />

He was an avid tennis player until an injury in 1940, and drank an [[Old fashioned (cocktail)|Old Fashioned]] with dinner.<ref name="Lessing-320" /> Politically, he was described by one of his associates as "a revolutionist only in technology – in politics he was one of the most conservative of men."<ref>Dreher (1976), page 208.</ref>

In 1955, Marion Armstrong founded the Armstrong Memorial Research Foundation, and participated in its work until her death in 1979 at the age of 81. She was survived by two nephews and a niece.<ref name="Esther">{{cite news |title=Esther Armstrong, 81, the Wife Of Inventor of FM Radio System |issn=0362-4331 |page=A13 |newspaper=The New York Times |date=August 10, 1979}}</ref>

== Awards ==
{| class="wikitable"
! Country
! Year
! Institute
! Award
! Citation
! {{Reference column heading}}
|-
| {{Flag|United States|1912}}
| 1917
| [[Institute of Radio Engineers]]
| [[IRE Medal of Honor]]
| "In recognition of his work and publications dealing with the action of the oscillating and non-oscillating audio"
| <ref>{{Cite web|title=E. H. Armstrong|url=https://corporate-awards.ieee.org/recipient/e-h-armstrong/|url-status=live|publisher=[[IEEE]]|archive-url=https://web.archive.org/web/20240513091008/https://corporate-awards.ieee.org/recipient/e-h-armstrong/|archive-date=2024-05-13|access-date=2024-05-13}}</ref>
|-
| {{Flag|United States|1912}}
| 1940
| [[ASME]]
| [[Holley Medal]]
|
| <ref>{{Cite web|title=Holley Medal|url=https://www.asme.org/about-asme/honors-awards/achievement-awards/holley-medal|url-status=live|publisher=[[ASME]]|archive-url=https://web.archive.org/web/20250814211139/https://www.asme.org/about-asme/honors-awards/achievement-awards/holley-medal|archive-date=2025-08-14|access-date=2025-11-05}}</ref>
|-
| {{Flag|United States|1912}}
| 1941
| [[Franklin Institute]]
| [[Franklin Medal]]
| "Invention of the superheterodyne circuit, the super-regenerator, and a system of wide-swing frequency modulation for communications"
| <ref>{{Cite web|title=Edwin H. Armstrong|url=https://fi.edu/en/awards/laureates/edwin-h-armstrong|url-status=live|publisher=[[Franklin Institute]]|archive-url=https://web.archive.org/web/20250329030716/https://fi.edu/en/awards/laureates/edwin-h-armstrong|archive-date=2025-03-29|access-date=2025-11-18}}</ref>
|-
| {{Flag|United States|1912}}
| 1942
| [[AIEE]]
| [[AIEE Edison Medal]]
| "For distinguished contributions to the art of electric communication, notably the regenerative circuit, the superheterodyne, and frequency modulation"
| <ref>{{Cite web|title=IEEE Edison Medal Recipients|url=https://corporate-awards.ieee.org/wp-content/uploads/edison-rl.pdf|url-status=live|publisher=[[IEEE]]|archive-url=https://web.archive.org/web/20241203160017/https://corporate-awards.ieee.org/wp-content/uploads/edison-rl.pdf|archive-date=2024-12-03|access-date=2024-12-10}}</ref>
|-
| {{Flag|United States}}
| 1951
| [[Western Society of Engineers]]
| [[Washington Award]]
| "For outstanding inventions basic to radio transmission and reception, and notable service to his country"
| <ref>{{Cite web|title=Recipients|url=https://www.washingtonaward.com/recipients/|url-status=live
|website=www.washingtonaward.com|archive-url=https://web.archive.org/web/20250715193421/https://www.washingtonaward.com/recipients/|archive-date=2025-07-15|access-date=2025-11-18}}</ref>
|}

== Commemorations ==
In 1980, Armstrong was inducted into the [[National Inventors Hall of Fame]], and appeared 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."<ref>{{cite web |title=Consumer Electronics Hall of Fame |url=http://www.ce.org/Events/Awards/357.asp |archive-url=https://web.archive.org/web/20100325153857/http://www.ce.org/Events/Awards/357.asp |website=Consumer Electronics Association (archived) |date=2000 |archive-date=25 March 2010 |access-date=14 May 2025 |url-status=dead}}</ref> 
He was posthumously inducted into the Wireless Hall of Fame in 2001.<ref>{{cite web | title=Edwin Armstrong | website=Wireless History Foundation  | date=April 25, 1999 | url=https://wirelesshistoryfoundation.org/edwin-armstrong/ | access-date=April 16, 2024}}</ref> [[Columbia University]] established the Edwin Howard Armstrong Professorship in the School of Engineering and Applied Science in his memory.<ref name="Columbia"/>

Philosophy Hall, the Columbia building where Armstrong developed FM, was declared a [[National Historic Landmark]]. [[Edwin H. Armstrong House|Armstrong's boyhood home]] in Yonkers, New York was recognized by the National Historic Landmark program and the [[National Register of Historic Places]], although this was withdrawn when the house was demolished.<ref name="nrhptext">{{cite web|last=Sheire|first=James|title=National Register of Historic Places Inventory/Nomination: Edwin H. Armstrong House|url=http://www.oprhp.state.ny.us/hpimaging/hp_view.asp?GroupView=10774|date=July 1975|access-date=January 25, 2008|url-status=dead|archive-url=https://web.archive.org/web/20110724052611/http://www.oprhp.state.ny.us/hpimaging/hp_view.asp?GroupView=10774|archive-date=July 24, 2011}} (includes 1 photo)</ref><ref name="nhlsum">{{cite web
 |url         = https://www.nps.gov/subjects/nationalhistoriclandmarks/edwin-h-armstrong-house.htm
 |title       = Edwin H. Armstrong House
 |access-date  = November 4, 2019
|work        = National Historic Landmark summary listing
 |publisher   = National Park Service
 |df          = mdy
}}</ref>

Armstrong Hall at Columbia was named in his honor. The hall, located at the northeast corner of [[Broadway (Manhattan)|Broadway]] and 112th Street, was originally an apartment house but was converted to research space after being purchased by the university. It is currently home to the [[Goddard Institute for Space Studies]], a research institute dedicated to atmospheric and climate science that is jointly operated by Columbia and the [[National Aeronautics and Space Administration]]. A storefront in a corner of the building houses [[Tom's Restaurant]], a longtime neighborhood fixture that inspired [[Susanne Vega]]'s song "[[Tom's Diner]]" and was used for establishing shots for the fictional "Monk's diner" in the "[[Seinfeld]]" television series.

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.

In 2005, Armstrong's regenerative feedback circuit and superheterodyne and FM circuits were inducted into the [[TECnology Hall of Fame]], an honor given to "products and innovations that have had an enduring impact on the development of audio technology."<ref>{{cite web|title=TECnology Hall of Fame, 2005|url=http://legacy.tecawards.org/tec/05TECnologyHOFdetails.html|website=TECawards.org|date=2005|access-date=December 12, 2024}}</ref>

==Patents==

E. H. Armstrong patents:

*{{US patent|2630497}} : "Frequency Modulation Multiplex System"
*{{US patent|2602885}} : "Radio Signaling"
*{{US patent|2540643}} : "Frequency-Modulated Carrier Signal Receiver"
*{{US patent|2323698}} : "Frequency Modulation Signaling System"
*{{US patent|2318137}} : "Means for Receiving Radio Signals"
*{{US patent|2315308}} : "Method and Means for Transmitting Frequency Modulated Signals"
*{{US patent|2295323}} : "Current Limiting Device"
*{{US patent|2290159}} : "Frequency Modulation System"
*{{US patent|2276008}} : "Radio Rebroadcasting System"
*{{US patent|2275486}} : "Means and Method for Relaying Frequency Modulated Signals"
*{{US patent|2264608}} : "Means and Method for Relaying Frequency Modulated Signals"
*{{US patent|2215284}} : "Frequency Modulation Signaling System"
*{{US patent|2203712}} : "Radio Transmitting System"
*{{US patent|2169212}} : "Radio Transmitting System"
*{{US patent|2130172}} : "Radio Transmitting System"
*{{US patent|2122401}} : "Frequency Changing System"
*{{US patent|2116502}} : "Radio Receiving System"
*{{US patent|2116501}} : "Radio Receiving System"
*{{US patent|2104012}} : "Multiplex Radio Signaling System"
*{{US patent|2104011}} : "Radio Signaling System"
*{{US patent|2098698}} : "Radio Transmitting System"
*{{US patent|2085940}} : "Phase Control System"
*{{US patent|2082935}} : "Radio Signaling System"
*{{US patent|2063074}} : "Radio Transmitting System"
*{{US patent|2024138}} : "Radio Signaling System"
*{{US patent|1941447}} : "Radio Telephone Signaling"
*{{US patent|1941069}} : "Radiosignaling"
*{{US patent|1941068}} : "Radiosignaling"
*{{US patent|1941067}} : "Radio Broadcasting and Receiving System"
*{{US patent|1941066}} : "Radio Signaling System"
*{{US patent|1716573}} : "Wave Signaling System"
*{{US patent|1675323}} : "Wave Signaling System"
*{{US patent|1611848}} : "Wireless Receiving System for Continuous Wave"
*{{US patent|1545724}} : "Wave Signaling System"
*{{US patent|1541780}} : "Wave Signaling System"
*{{US patent|1539822}} : "Wave Signaling System"
*{{US patent|1539821}} : "Wave Signaling System"
*{{US patent|1539820}} : "Wave Signaling System"
*{{US patent|1424065}} : "Signaling System"
*{{US patent|1416061}} : "Radioreceiving System Having High Selectivity"
*{{US patent|1415845}} : "Selectively Opposing Impedance to Received Electrical Oscillations"
*{{US patent|1388441}} : "Multiple Antenna for Electrical Wave Transmission"
*{{US patent|1342885}} : "Method of Receiving High Frequency Oscillation"
*{{US patent|1336378}} : "Antenna with Distributed Positive Resistance"
*{{US patent|1334165}} : "Electric Wave Transmission" (Note: Co-patentee with [[Mihajlo Pupin]])
*{{US patent|1113149}} : "Wireless Receiving System"
<ref>{{citation |title=U.S. Patent and Trademark Office Database Search: Edwin H. Armstrong |url=http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.htm&r=0&p=1&f=S&l=50&Query=IN%2FArmstrong-Edwin-H&d=PALL |access-date=July 16, 2017 |archive-date=March 12, 2018 |archive-url=https://web.archive.org/web/20180312022556/http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.htm&r=0&p=1&f=S&l=50&Query=IN%2FArmstrong-Edwin-H&d=PALL |url-status=dead }}</ref> U.S. Patent and Trademark Office Database Search

The following patents were issued to Armstrong's estate after his death:
*{{US patent|2738502}} : "Radio detection and ranging systems" 1956
*{{US patent|2773125}} : "Multiplex frequency modulation transmitter" 1956
*{{US patent|2835803}} : "Linear detector for subcarrier frequency modulated waves" 1958
*{{US patent|2871292}} : "Noise reduction in phase shift modulation" 1959
*{{US patent|2879335}} : "Stabilized multiple frequency modulation receiver" 1959
<ref>Kraeuter, David. Radio Patent Lists and Index 1830-1980, 2001, p. 23</ref>

==See also==
{{Portal|Radio}}
*[[Edwin Howard Armstrong award|Awards named after E. H. Armstrong]]
*[[Grid-leak detector]]

==Notes==
{{Reflist|30em}}

==References==
* {{Citation |title=Armstrong's fight for FM broadcasting: one man vs big business and bureaucracy |first=Don V. |last=Erickson |publisher=University of Alabama Press |year=1973 |isbn=0-8173-4818-2}}
* Frost, Gary L. (2010), ''Early FM Radio: Incremental Technology in Twentieth-Century America.'' Baltimore: Johns Hopkins University Press, 2010. {{ISBN|0-8018-9440-9}}, {{ISBN|978-0-8018-9440-4}}.
* {{Citation |title=Man of High Fidelity: Edwin Howard Armstrong, a biography |last=Lessing |first=Lawrence |author-link=Lawrence Lessing |year=1956 |publisher=Lippincott |location=Philadelphia|url=https://archive.org/details/in.ernet.dli.2015.189098/page/n2/mode/1up}}
* {{Citation |title=Empire of the air: the men who made radio |first=Tom |last=Lewis |publisher=Edward Burlingame Books |year=1991 |isbn=0-06-098119-9 |location=New York}}
* {{cite book|title=Who Was Who in American History - the Military|date=1975|publisher=Marquis Who's Who|location=Chicago|isbn=0837932017}}
* {{Citation |title=The Master Switch |last=Wu |first=Tim |author-link=Tim Wu |year=2010 |publisher=Alfred A. Knopf |location=New York |isbn=978-0-307-26993-5 |url=https://archive.org/details/masterswitchrise00wuti_0 }}

==Further reading==
* Ira Brodsky. ''The History of Wireless: How Creative Minds Produced Technology for the Masses.'' St. Louis: Telescope Books, 2008.
* [[Ken Burns]]. [https://www.pbs.org/kenburns/empire/ Empire of the Air] {{Webarchive|url=https://web.archive.org/web/20181206030242/https://www.pbs.org/kenburns/empire/ |date=December 6, 2018 }}. Documentary that first aired on [[Public Broadcasting Service|PBS]] in 1992.
*{{cite encyclopedia | last= Süsskind |first= Charles |title= Armstrong, Edwin Howard |encyclopedia= [[Dictionary of Scientific Biography]] |pages= 287–288 | publisher=Charles Scribner's Sons |location= New York |year= 1970 |isbn= 0-684-10114-9}}

==External links==
{{Commons category}}
{{Wikiquote}}
* {{Internet Archive author |sname=Edwin Howard Armstrong}}
* [http://www.armstrongmemorialfoundation.org/ Armstrong Memorial Research Foundation] – The Armstrong Foundation disseminates knowledge of Armstrong's research and achievements
* [http://users.erols.com/oldradio/ Houck Collection] – A collection of images and documents that belonged to Armstrong's assistant, Harry W. Houck, which have been annotated by Mike Katzdorn.
* [https://findingaids.library.columbia.edu/ead//nnc-rb/ldpd_4078687 Rare Book & Manuscript Library Collections] – A collection of images and documents at Columbia University
* [https://web.archive.org/web/20080509070320/http://world.std.com/~jlr/doom/armstrng.htm Biography]
* [https://www.oldradio.com/archives/people/armstrong.htm The Broadcast Archive] – A brief biography by [[Donna Halper]]
* Ammon, Richard T., "''[http://www.superhets.info The Rolls Royce Of Reception] : Super Heterodynes – 1918 to 1930''".
* IEEE History Center's [https://ethw.org/Edwin_H._Armstrong Edwin H. Armstrong] : Excerpt from "The Legacy of Edwin Howard Armstrong," by J. E. Brittain Proceedings of the IEEE, vol. 79, no. 2, February 1991
* Hong, Sungook, "''[https://web.archive.org/web/20050215034606/http://www.ieee.org/organizations/history_center/Che2004/Hong.pdf A History of the Regeneration Circuit: From Invention to Patent Litigation]''" University, Seoul, Korea (PDF)
* [https://antiqueradios.com/superhet/ Who Invented the Superhetrodyne?] {{Webarchive|url=https://web.archive.org/web/20240424040101/https://antiqueradios.com/superhet/ |date=April 24, 2024 }} The history of the invention of the superhetrodyne receiver and related patent disputes
* Yannis Tsividis, "[http://www.columbia.edu/cu/alumni/Magazine/Spring2002/Armstrong.html Edwin Armstrong: Pioneer of the Airwaves]", 2002. A profile on the web site of [[Columbia University]], Armstrong's alma mater
{{IEEE Edison Medal Laureates 1926-1950}}
{{IEEE Medal of Honor Laureates 1917-1925}}

{{Authority control}}

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