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Armstrong, Edwin Howard

radio electrical carrier amplitude

(1890–1954) US radio engineer.

Many teenagers build radio receivers; Armstrong was unusual in also making a transmitter before he became a student of electrical engineering at Columbia. Then, during the First World War, he worked on the problem of locating aircraft by detecting the stray radio emission from their ignition systems; a side-result was his development of the superheterodyne circuit, which made radio tuning much easier and helped make radio popular. From 1934 he taught electrical engineering at Columbia and by 1939 he had devised a major advance in radio transmission: FM.

Previously, radio signals conveyed speech or music by changes in the amplitude of the carrier radio waves (amplitude modulation, AM). The snag of this is that electrical storms and appliances introduce random noise (static). Armstrong’s method was to vary the carrier signal by changes in frequency (frequency modulation, FM) which is largely free from interference. This requires use of high frequencies that have only a limited range, but it has become the preferred mode for radio and TV use.

Armstrong, Edwin Howard (1890-1954) [next] [back] Armstrong(born Hardin), Lil(ian)

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