Sunday, June 10, 2012

Edwin Armstrong -the FM inventor

1935 June 11- Inventor Edwin Armstrong gives the first public demonstration of FM broadcasting in the United States at Alpine, New Jersey.

Edwin Armstrong was studying at Columbia University in 1912 when he devised a feedback circuit that brought in signals with a thousandfold amplification. This circuit was the heart of all radio and television broadcasting. It earned him the Franklin Medal, the highest U.S. scientific honor. His 1933 invention of circuits that produced the carrier waves for frequency modulation made FM radio possible.

Edwin Howard Armstrong was born on December 18, 1890 in the Chelsea neighborhood of New York City. His father was the president of the American office of Oxford University Press and his mother was a former school teacher. Armstrong was a shy child who was interested engines and other mechanical things. In 1902 he moved with his family to Yonkers, New York. A case of rheumatic fever left him with a tic in one eye. At age 14, inspired by the work of Guglielmo Marconi, Armstrong decided at he would be an inventor and built a wireless apparatus in the attic of his family's home and constructed a 125 foot tall antenna mast on his family's lawn. Armstrong attended public schools in Yonkers, graduating from Yonkers High School. After graduation he commuted by motorcycle to the engineering school at Columbia University.

At Columbia Armstrong studied under inventor Micheal Pupin and during his junior year invented the regenerative circuit. The regenerative circuit was an improvement on the audion, a radio tube circuit that was used in wireless receivers and invented by Lee DeForest. With the audion the receiver signal was weak and required the use of headphones in order to hear the broadcast. Armstrong's regenerative circuit amplified the signal and loudspeakers could be used to listen to the broadcast. The regenerative circuit could also be used to create radio transmitters. Armstrong graduated with a engineering degree in 1913 and filed for a patent for the regenerative circuit. After graduation he stayed at Columbia teaching and working as Pupin's assistant.

During the first world war Armstrong served in the United States Army Signal Corps. He was sent to Paris, France where he worked to intercept enemy shortwave radio signals setting up his receiver on the Eiffel Tower. While serving in the Army he developed his second major invention, the superheterodyne circuit, which made radio receivers easier to tune and is still used today. Armstrong rose to the rank of major and was awarded the French Legion of Honor ribbon. After the war he returned to Columbia where he eventually succeeded Pupin and in 1920 he sold the rights to his two inventions to Westinghouse. He also sold the rights for another invention, the super regenerative circuit, to newly founded RCA for a large block of stock.

As the 1920s wore on Armstrong increasingly became involved in patent infringement lawsuits. Lee DeForest filed a patent on the regenerative circuit a year after Armstrong's patent and sold the rights to AT&T. AT&T sued Armstrong and the case went through a dozen courts eventually reaching the United States Supreme Court, where Armstrong lost his case due to the justices' misunderstanding of technical details of the circuit. The Institute of Radio Engineers, which had awarded its first gold medal to Armstrong, refused to accept the verdict and take back its medal.

While the legal battle continued Armstrong was working on another invention. Instead of using radio wave amplitude modulation (AM radio) for tuning he developed a receiver that was tuned by radio wave frequency modulation (FM radio). Frequency modulation reduced background noise allowing for clearer reception. The great depression of the 1930s made it impossible for Armstrong to sell his new invention and it was not until 1940 that Armstrong built the first FM station in Alpine, New Jersey, but it was not for another two years that the Federal Communications Commission allocated frequencies to Armstrong.

FM radio did not take off until after World War II when Armstrong again found his patents infringed. Being ill, bereft of money, and facing another long legal battle Armstrong committed suicide on new years eve of 1954, jumping out the window of his New York City apartment.

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