Lee De Forest

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American physicist and inventor (1873–1961)

De Forest, who was born in Council Bluffs, Iowa, was interested in science from the age of 13. His father, a congregational minister, wanted him to study for the Church, but De Forest refused, going instead, in 1893, to the Sheffield Scientific School at Yale University. His PhD thesis, Hertzian Waves from the Ends of Parallel Wires (1899), was probably the first PhD thesis on radio in America, and drew on the work of Heinrich Hertz and Guglielmo Marconi. While working for the Western Electric Company in Chicago, he developed an electrolytic detector and an alternating-current transmitter.

In 1907 De Forest patented the Audion tube, a thermionic grid-triode vacuum tube that was a very sensitive receiver of electrical signals. This invention was crucial to the development of telecommunications equipment. In 1912 he had the idea of ‘cascading’ these to amplify high-frequency radio signals, making possible the powerful signals needed for long-distance telephones and for radio broadcasting. His invention formed the basis of radio, radar, telephones, and computers until the advent of solid-state electronics.

Throughout his career De Forest pushed for the acceptance of radio broadcasting. He was not a very good business manager, however, and had to sell many of his patents. Later he worked on a sound film system that was similar to the one eventually adopted. In the 1930s he designed Audion diathermy machines for medical use and during World War II he worked on military research at the Bell Telephone Laboratories.

The American inventor Lee De Forest (1873-1961) pioneered in radio, both in developing broadcasting and in inventing the audion. He is considered one of the fathers of radio.

Lee De Forest was born in Council Bluffs, Iowa, in 1873, where his father was a minister. While Lee was still a boy, his father became the president of the College for the Colored in Talladega, Ala. Because of his father's association with African Americans, young Lee was shunned by playmates and sought relief from his loneliness in invention and mechanics. He took bachelor of science and doctor of philosophy degrees from Yale in 1896 and 1899. He then went to work for the Western Electric Company in Chicago.

During the 1890s Guglielmo Marconi transmitted radio waves over increasing distances; his work culminated in 1901 with a transatlantic message. The new field of radio attracted many inventors, among them De Forest. In 1910 he literally electrified the musical world by broadcasting the voice of Enrico Caruso by radio. In 1916 De Forest made what he believed to be the first news broadcast by radio.

The greatest single contribution De Forest made to the field, however, was his invention of the triode, or audion, as he called it, for which he received a patent in 1908. One of the major goals of inventors was to come up with a more powerful and sensitive detector, or receiver. In 1904 John Ambrose Fleming, a consultant to the Edison Electric Light Company, patented a two-electrode vacuum tube which he called a thermionic valve. Acting between the two electrodes, one of which was heated, the oscillating radio waves were made unidirectional. De Forest's contribution, which he claimed was made in ignorance of Fleming's earlier work, was to add a third element, thus converting the diode to a triode. This new element was a grid (or zigzag piece of wire) placed between the other two. Although no one, including the inventor himself, realized the importance or the exact action of the audion, it proved to be the basis of all subsequent radio development because it could be used to send, receive, or amplify radio signals better than any other device.

In 1902 De Forest became vice president of the De Forest Wireless Telegraph Company and in 1913 vice president of the Radio Telephone Company and the De Forest Radio Company. He worked on other electrical problems, including talking motion pictures and television, and eventually received over 300 domestic and foreign patents. He made and lost four fortunes during his lifetime and was extensively engaged in court litigation with such formidable foes as Irving Langmuir of the General Electric Company and Edwin Armstrong, with whom he disputed invention of the feedback circuit. This last dispute was decided in favor of De Forest in 1934. He retired to a private research laboratory in Hollywood, Calif.

Further Reading

De Forest's autobiography is Father of Radio (1950). A more balanced account of his contributions is the standard history of radio, William R. Maclaurin, Invention and Innovation in the Radio Industry (1949). The business side of radio is covered in Erik Barnouw, A History of Broadcasting in the United States (1966).