Haraden Pratt

By Bob Morrison

04 April, 2006

Sixty five years ago this month, the PROCEEDINGS OF THE INSTITUTE OF RADIO ENGINEERS (IRE) included a paper by Haraden Pratt on an aircraft radio beacon. By the time his paper was published, he was an engineer with Mackay Radio and Telegraphy Company of New York City, but he had worked at the National Bureau of Standards when the beacon system was under development. In addition to his technical contributions to radio, Pratt served the IRE and the IEEE in various capacities for more than forty year.

Pratt’s May 1929 paper provided a mathematical analysis of field intensity as a function of direction from beacon transmitters located on the ground and maintained by the government. Each transmitter employed two loop antennas and produced two beams which could be picked up by an aircraft receiver with a visual indicator designed to show the pilot whether the plane was on course. If the plane were on the proper course it received two signals of equal intensity on an indicator with two vibrating reeds which gave the appearance of two vertical white lines, If the lines were equal in length, the plane was on course, but, if the right line seemed longer, the plane was off course to the right. The system had a range of about 200 mi and the receiver weighed less than 15 lb. Pratt himself had participated in test flights using the beacon during 1927.

Pratt was born in San Francisco, CA, in 1891 and graduated from the University of California in 1914. Both his parents were telegraph operators and he learned Morse code at an early age, He worked briefly as a wireless operator on ships before entering college and during summers while he was an undergraduate, Soon after his graduation, he joined the American Marconi Company and helped to install a transpacific station in Bolinas, CA. In 1915 he left Marconi to take a job as a radio expert at the Mare Island Navy Yard. He installed radio equipment on Navy ships and installed and maintained shore stations on the West coast until 1918 when he was transferred to Washington, DC.

In 1920, Pratt joined the Federal Telegraph Company in Palo Alto, CA, and designed a system for commercial radio telegraph service. In 1926, the Congress passed the Air Commerce Act which provided funds for development of radio aids to air navigation. J. Howard Dellinger of the Bureau of Standards offered Pratt the opportunity to help develop a suitable system and he worked with Harry Diamond and others on the radio beacon during 1927-1928. In 1928, Pratt accepted an offer to become chief engineer of the recently organized Mackay Radio and Telegraph Company which subsequently was acquired by the International Telephone and Telegraph Company. He remained with ITT until 1951 and became a Vice President and General Manager.

Pratt joined the IRE in 1914 and became a member of the IRE Standardization Committee in 1928. He became an IRE Director in 1935, served as the President of the IRE in 1938, and was Secretary of the Institute from 1943 to 1965. He was awarded the IRE Medal of Honor in 1944 and the Founder’s Award in 1960. Pratt served on 25 Institute committees and became the first Chairman of the IRE History Committee when it was formed in 1956. The Haraden Pratt .Award was established in 1971 by the IEEE to recognize individuals for their service to the Institute.

During World War II, Pratt was a Division Chief in the Office of Scientific Research and Development and was Chairman of the Radio Technical Planning Board from 1945 to 1949. He was an official observer of the atomic bomb tests at Bikini in 1946. He served as telecommunications advisor to Presidents Truman and Eisenhower during 1951-1953. Pratt was a Vice President of the American Cable and Radio Company from 1953 to 1958. He died in August 1969 at age 78.

James E. Brittain
School of History, Technology, and Society
Georgia Institute of Technology

Submitted by Dick Reiman, Historian