Edwin Howard Armstrong (December 18, 1890 – February 1, 1954) 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 U.S. Army Signal Corps during World War I and was often referred to as "Major Armstrong" during his career. 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. 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
Edwin Howard Armstrong was born on December 18, 1890, in Chelsea, New York City, the eldest of three children of John Armstrong and Emily Smith. 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. 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.Man of High Fidelity by Lawrence Lessing (1956) p. 22 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.Lessing 1956, p. 23 The family was comfortably middle class.
At the age of eight, Armstrong contracted Sydenham's chorea (then known as Saint 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.Lessing 1956, p. 26 To improve his health, the Armstrong family moved to a house overlooking the Hudson River, at 1032 Warburton Avenue in Yonkers. The Smith family subsequently moved next door.Lessing 1956, p. 24 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.Lessing 1956, p. 27 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.
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 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."What Everyone Should Know About Radio History: Part II" by Prof. J. H. Morecroft, Radio Broadcast, August 1922, pp. 294–302. 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.Empire of the Air by Tom Lewis, 1991, pp. 60–61. 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.
During World War I, Armstrong served in the Signal Corps as a captain and later a major.
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.The Legacies of Edwin Howard Armstrong, "E. H. Armstrong" by Thomas Sykes, 1990, p. 22. 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.
Early work Regenerative circuit
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) "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.DeForest Radio Co. v. General Electric Co., 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." 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."Operating Features of the Audion" by E. H. Armstrong, Electrical World, December 12, 1914, pages 1149-1152. 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. Further investigation revealed that when the feedback was increased beyond a certain level a vacuum-tube would go into 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, and in late 1913 applied for patent protection covering the regenerative circuit. On October 6, 1914, was issued for his discovery.Lewis (1991), pages 77, 87. 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 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.Ibid., page 192.
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.Invention and Innovation in the Radio Industry by W. Rupert Maclaurin, 1949, page 122. 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.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.
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.Douglas (1991), pages 193-198, 203.