Jacqueline Hochheiser, Corporate Communications
Introduction
Edwin Howard Armstrong was an American electrical engineer best known for having invented foundational electronic circuits still used in moder radio, radar and television. These inventions include the regenerative circuits, the superheterodyne circuit, and the FM radio. The regenerative circuit was the first amplifying receiver and the first reliable continuous-wave transmitter, while his crowning achievement, the FM radio, revolutionized the way people listened to news and music.
Early Life & Education
Armstrong was born on December 18th, 1890 in Chelsea, New York as the eldest of three children born to John Armstrong and Emily Smith. Armstrong’s father began working at a young age for the American branch of the Oxford University Press, which published bibles and classical works. He was eventually promoted to vice president of the branch, and the family lived a comfortable middle-class life.
At 8 years old, Armstrong developed Sydenham’s Syndrome, a disorder displaying uncontrollable rapid jerking movements of the face, hands and feet. Due to the illness, he withdrew from school and was home tutored for two years. Overtime, the homeschooling and his self-consciousness of his tic made him socially withdrawn. Even so, from a young age, Armstrong showed an affinity for electrical and mechanical devices, and even constructed a makeshift antenna in his parents’ backyard.
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. He also had the opportunity to study under Michael Pupin, a renowned electrical engineer and physicist at Hartley Laboratories.
He graduated with an electrical engineering degree in 1913, and shortly after when the United States got involved in WWI, Armstrong served in the Signal Corps, a branch of the U.S. Army responsible for establishing and managing the communication and information systems for the combined armed forces. He started as a captain and eventually made his way up to major over the course of his service.
Influential Inventions
Regenerative Circuit
Armstrong created and patented many inventions during his time, however, there are three that are considered his most influential. The first being the regenerative circuit, which he invented and patented while he was still an undergraduate student at Columbia.
After Lee DeForest had invented the audion tube, which was used in early telegraph applications, Armstrong developed a keen interest in how audion tubes worked and carried out his own home-grown experiments. His discoveries uncovered that employing positive feedback (regeneration), produced amplification hundreds of times more powerful than what was previously possible.
The amplified signals were now strong enough that loudspeakers could be used to project the sound instead of headphones. It was also determined that if the feedback was increased beyond a certain level, the vacuum tube would go into oscillation and could be used as a continuous-wave radio transmitter. In late 1913, Armstrong applied for a patent for his regenerative circuit and received it in October of 1914.
Superheterodyne Circuit
Armstrong developed his superheterodyne circuit while he was serving in the army during WWI. The U.S. entered the war in April of 1917, and Armstrong joined the Signal Corps soon after. He served at a laboratory in Paris, France to help develop radio communications for the Allied war effort. The superheterodyne circuits made radio receivers more sensitive and selective and is still used widely today.
The main factor of the superheterodyne approach is the mixing of the incoming radio signal with a locally generated, different frequency signal within the radio set: that circuits is called a mixer. The result is a fixed, unchanging intermediate frequency (IF) signal that is easily amplified and detected by following circuit stages. Armstrong also applied for a patent for this circuit, which was granted in 1920.
FM Radio
FM, or wideband frequency modulation radio was developed by Armstrong in 1933. Before FM radio, there was amplitude modulation (AM) radio, which was the only form of radio available. AM radio works by varying the amplitude, or power of radio waves to carry voices or music by matching the two frequencies. FM revolutionized the radio because it varied, or modulated the waves’ frequency over a wide band of frequencies.
This method created a carrier wave that natural static could not break into, thus creating a clear, practical method of high-fidelity broadcasting with a wider frequency range. However, the new system required a whole new system including different transmitters and receivers. Because of this, the infrastructure of radio stations had to change. In order to prove his confidence in the FM radio, Armstrong built the first full-scale FM radio station in 1939 for more than $300,000.
Late Life & Death
The list of Armstrong’s major honors is long and includes many prestigious rewards. Some of these include the Medal of Honor from the Institute of Radio Engineering (1917), the Chevalier de la Legion d’Honneur from the French Government (1919), the first ever Armstrong Award from the Radio Club of America (1935), Columbia’s Egleston Medal (1939), the Holley Medal from the American Society of Mechanical Engineers (1940) and many more.
Despite these achievements, Armstrong met a tragic fate. In his later years, he spent much of his fortune in legal battles fighting patent infringements. The stress and the loss of money took a toll on Armstrong’s mental health, which began to rapidly decline during this time.
On the night of January 31st, Armstrong tragically committed suicide, passing away at just 64 years old. He had jumped from the window of his River House apartment building in New York City. He fell to his death thirteen floors below. Regardless of his unhappy and sudden ending, Armstrong left a permanent mark on the RF industry and revolutionized communications methods.
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