Edwin H. Armstrong

American electrical engineer and inventor

• Born: December 18, 1890
• Birthplace: New York, New York
• Died: January 31, 1954
• Place of death: New York, New York

From the infancy of radio, Armstrong was the leading edge of its technical development, inventing the basic circuitry of modern AM-FM broadcasting. His finest invention, however, was the wideband frequency modulation (FM) system of broadcasting, which provided a static and distortion-free technique that was far superior to AM.

Early Life

Edwin H. Armstrong was born to a middle-class were chosen family. His youth was a reflection of America’s fascination with the revolutionary technical innovations then transforming the nation. As a boy, Armstrong displayed a markedly precocious ability with things mechanical and developed a strong interest in trains and locomotives. He read voraciously of the then-popular Horatio Alger “Rags to Riches” adventure books for boys as well as the new science-fiction stories. He declared in later life that his career in science began at fourteen, when, after reading about the exploits of inventor Guglielmo Marconi, he decided to become an inventor himself. Fabricating his own coherers, detectors, and hand-wound coils, he had, by his midteens, built his own spark-based station for listening to wireless broadcasts. Radio had become his consuming interest by the time he entered Columbia University to study electrical engineering. While working there in the graduate radio laboratory, he was exposed to Lee de Forest’s then-recent invention of the Audion, or three-element vacuum tube. Although de Forest had at that time used the tube only for the amplification of audio signals, Armstrong immediately saw the possibility of using the tube to generate radio frequency signals, and in a short time he developed the regenerative or feedback amplification circuit. Because he was unable to persuade his father to fund a prompt patent application, his claim for the invention was delayed until January, 1913, when a drawing of the regenerative circuit was notarized. By this time, de Forest had realized this important application of the Audion tube and filed his own patent, followed by Alexander Meissner in Germany and C. S. Franklin in England.

Thus, when Armstrong was graduated from Columbia University in May, 1913, he found himself embroiled in an international dispute over patent rights to a major invention, defending his position against some of the greatest names in radio. This legal dispute over patent rights was the beginning of a pattern that would follow him for the remainder of his life.

Life’s Work

Armstrong’s time during his twenties was spent in bitter litigation with de Forest. Although de Forest eventually won the patent, de Forest continued the deep animosity between the two by maintaining interference proceedings for the next ten years.

During World War I, Armstrong served in Paris as a U.S. Signal Corps officer attached to the radio laboratory of the École Militaire. By his later account, he was there struck by the difficulty of building triode amplifiers capable of intercepting the extremely weak, shortwave signals then used by the Germans in their field communications. The amplifiers in use could not sustain the power levels required without breaking into self-driven oscillation from unwanted feedback.

Armstrong’s solution was to convert the incoming signal to a fixed frequency by heterodyning it to a local oscillator in the receiver and obtaining the needed sensitivity by processing the signal at the lower imposed frequency, where stability was more readily secured. It was an elegant design and has proved basic to all later receiver circuitry. In the summer of 1920, after additional research at Columbia University, he was awarded the United States patent for the superheterodyne receiver circuit.

Although he possessed the most fundamental receiver and transmitter patents, Armstrong’s position was by no means secure. His patent for the regenerative circuit was under attack by de Forest in the U.S. Patent Office, incurring heavy legal expenses. In the fall of 1920, he sold the superheterodyne receiver patent to Westinghouse for $335,000 in cash, with an additional $200,000 to be paid if he won the interference proceedings against de Forest.

While setting up a courtroom demonstration in 1921, he noticed an unusual mode of radio detection and, following experimental development, filed patent application for the superregenerative detector, which was awarded in 1922. In 1924, his patent for the superheterodyne circuit was challenged by the American Telephone and Telegraph Company (AT&T), which possessed the American rights to the patent of Lucien Levy, a French radio engineer. Levy claimed to have invented the superheterodyne receiver during the war while stationed at the École Militaire and that Armstrong had stolen the invention while serving there in the signal corps. Armstrong spent his energy and personal financial resources defending the patent position in the courts against bitter professional and sometimes personal attacks. Although he retained rights to the regenerative circuits, he ultimately lost all the claims for the superheterodyne circuit to Levy, backed by AT&T.

During these legal battles, from 1928 to 1933, he developed, with little assistance, his most critical invention, the wideband frequency modulation (FM) system of broadcasting, which provided a static and distortion-free technique that was far superior to AM. In the winter of 1933, he was awarded four patents that completely covered the FM system and which established him as its sole inventor. As the newly appointed professor of electrical engineering at Columbia University, he announced his invention to the world by reading a paper before the Institute of Radio Engineers and surprising his audience with a demonstration broadcast from an experimental station he operated with the help of a friend. His system was obviously superior to any AM system in use, yet its introduction was met with the skepticism of industry, which had invested heavily in AM broadcasting. Much of the remainder of his life was spent in trying to have FM adopted as the prime radio broadcasting system. He refined the techniques, set up stations, and traveled extensively, but with little result.

During World War II, he developed FM units for military communications, demonstrated long-range FM signaling, and worked on continuous-wave FM radar. Harassed by seemingly never-ending patent litigation and frustrated by the slow adoption of his FM broadcasting system, Armstrong committed suicide in New York on January 31, 1954.

Significance

Armstrong’s career spanned the golden age of radio development and broadcasting and reflected the spirit of the individual scientific pioneer that was typical of the early twentieth century. His work, from his undergraduate days, was always on the very basic phenomena of radio operations, his early contributions making possible the dream of voice radio transmission.

Much of his energy in the later years of his life was spent fighting challenges to his patents. If this time could have been devoted to invention and research, his scientific output could have been much higher. Despite this drain on him, he invented some of the most important circuits of modern radio, his creative output spanning the whole of his career.

Although he died feeling frustrated and unrecognized, the world has since seen the adoption of his systems as the standard of broadcasting and his ranking as one of the great scientists of modern electronics. His awards include the First Medal of Honor from the Society of Radio Engineers, the Franklin Medal, and the United States Medal of Merit. He is one of twenty world scientists honored in the Pantheon of the Union Internationale des Télécommunications in Geneva.

Bibliography

Aitken, Hugh G. J. The Continuous Wave: Technology and American Radio, 1900-1932. Princeton, N.J.: Princeton University Press, 1985. The best history of the development of radio available. Covers Armstrong’s patent and business dealings in depth as well as his impact on the development of the Radio Corporation of America (RCA) and Westinghouse as the dominant companies of early radio. Very well researched and documented, both historically and technically.

‗‗‗‗‗‗‗. Syntony and Spark: The Origins of Radio. Reprint. Princeton, N.J.: Princeton University Press, 1985. An excellent chronological history of the technical evolution of radio. Gives a broad picture of Armstrong’s technical innovations and how they affected the rapid pace of radio’s development at the time.

Evans, Harold, with Gail Buckland and David Lefer. They Made America: From the Steam Engine to the Search Engine, Two Centuries of Innovators. New York: Little, Brown, 2004. Armstrong is one of seventy American inventors and entrepreneurs who are profiled in this book.

Hamilton, Neil A. Lifetimes: The Great War to the Stock Market Crash, American History Through Biography and Primary Documents. Westport, Conn.: Greenwood Press, 2002. A biographical encyclopedia for high school students that includes essays about significant Americans. Contains an essay about Armstrong.

Lessing, Lawrence. Man of High Fidelity: Edwin Howard Armstrong. Philadelphia: J. B. Lippincott, 1956. The only biography yet written on the life of Armstrong, and the only source for information on his private life. Well written but sympathetic toward Armstrong’s difficulties. Provides a more personable view of the legal charges and accusations against Armstrong.

Lewis, Tom. Empire of the Air: The Men Who Made Radio. New York: Edward Burlingame Books, 1991. This companion volume to a television documentary of the same name focuses on the role played by Armstrong, Lee de Forest, and David Sarnoff in the creation of radio in the United States.

‗‗‗‗‗‗‗. “Radio Revolutionary.” American Heritage of Invention and Technology 1 (Fall, 1985): 34-41. A sympathetic but accurate brief account contrasting his tragic life with his triumphant inventions, especially FM.