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History of Science, Mathematics, Technology, #171


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  171.  Harold Miller Lewis (1893-1978).  Laboratory notebook, recording Edwin H. Armstrong's discovery of superheterodyne reception. Autograph manuscript, 137 pp. Paris, July 21, 1918-January 8, 1919. -- RBML, Edwin Howard Armstrong Papers (See fuller description below.)
 
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Edwin Howard Armstrong (1890-1954) is the largely unsung electrical engineer and inventor of three of the basic electronic circuits underlying all modern radio, radar, and television. Upon graduating from high school, Armstrong began to commute by motorcycle to Columbia University's school of engineering. In the summer of 1912, while a junior at Columbia, he made his first major invention: a new regenerative circuit in which part of the current at the plate was fed back to the grid to strengthen incoming signals. This single circuit yielded not only the first radio amplifier but also the key to the continuous-wave transmitter that is still at the heart of all radio operations. Armstrong received his engineering degree in 1913, filed for a patent, and returned to Columbia as an instructor and as assistant to the professor and inventor, Michael Pupin.

During World War I, Armstrong was commissioned a Captain and sent to Paris. While working under his direction in the Paris laboratory of the U.S. Signal Corps, Corporal Harold M. Lewis kept this notebook in which he recorded the invention of Armstrong's superheterodyne circuit, the basis for most radio, television and radar receivers. On August 13, 1918, Armstrong first explained to Lewis his new short wave amplification system; the complete circuit designs and the first working model were finished between August 14 and September 3, 1918. Thus, Armstrong had created a circuit capable of handling radio signals at much higher frequencies than were then possible. Lewis went on to a career in radio engineering and patented nearly sixty inventions of his own. Upon the success of early radio broadcasting after the war, Armstrong became a millionaire, but continued at Columbia University as a professor and eventual successor to Pupin. In 1941 he was given the highest honor in U.S. science, the Franklin Medal.

In 1933, Armstrong brought forth a wide-band frequency modulation (FM) system that in field tests gave clear reception through the most violent storms and, as a dividend, offered the highest fidelity sound yet heard in radio. But in the depressed 1930s the major radio industry was in no mood to take on a new system requiring basic changes in both transmitters and receivers. Armstrong found himself blocked on almost every side. It took him until 1940 to get a permit for the first FM station, erected at his own expense, on the Hudson River Palisades at Alpine, N.J. It would be another two years before the Federal Communications Commission granted him a few frequency allocations. Armstrong spent the rest of his life fighting infringements on his patents. Drained of resources and exhausted, Armstrong committed suicide on January 31, 1954. His estate eventually won $10,000,000 from multiple corporations in patent infringement actions. The Armstrong Papers were given to Columbia in 1977 by the Armstrong Memorial Research Foundation.

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