From 1915 to 1920 Pratt was a radio aide to the United States Navy, leading its radio laboratory and engineering at Mare Island Navy Yard, California. In this role he installed radio equipment on Navy ships and maintained West Coast shore stations until 1918, when he moved to Washington, D.C., to take charge of the construction and maintenance of all high-power Navy radio stations.
In 1928 Pratt became chief engineer of the Mackay Radio and Telegraph Company, subsequently acquired by the International Telephone and Telegraph Company (ITT), where he eventually became vice president and general manager. During World War II, Pratt served as Division Chief in the Office of Scientific Research and Development and was Chairman of the Radio Technical Planning Board 1945–1949, and in 1946 was an official observer of the Bikini atomic bomb tests. He remained with ITT until 1951 when he served from 1951 to 1953 as telecommunications advisor to Presidents Truman and Eisenhower. Pratt was vice president of the American Cable and Radio Corporation from 1953 to 1958.
Pratt joined the Institute of Radio Engineers (IRE), became an IRE Director in 1935, served as president of the IRE in 1938, and was its secretary from 1943 to 1965. He was awarded the IRE Medal of Honor in 1944 "in recognition of his engineering contributions to the development of radio, of his work in the extension of communication facilities to distant lands, and of his constructive leadership in Institute affairs," and the Founder's Award in 1960. The IEEE Haraden Pratt Award was established in 1971 in his honor. His papers are archived at the Bancroft Library, University of California, Berkeley.
J. H. Dellinger and Haraden Pratt, "Development of Radio Aids to Air Navigation," Proceedings of the Institute of Radio Engineers, 16 (July 1928): pages 900–902.
Haraden Pratt and Harry Diamond, "Receiving Sets For Aircraft Beacon and Telephony," Bureau of Standards Journal of Research vol. 1, no. 4 (October 1928): page 549.
