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Both the Allies and Axis powers used radar in World War II, and many important aspects of this conflict were greatly influenced by this revolutionary new technology.〔Brown, Louis; ''A Radar History of World War II'', Inst. of Physics Publishing, 1999〕 The technology of radio-based detection and tracking evolved independently in a number of nations during the mid 1930s.〔Watson, Raymond C. Watson, Jr.; ''Radar Origins Worldwide: History of Its Evolution in 13 Nations through World War II'', Trafford Publishing, 2009〕 At the outbreak of war in September 1939, both Great Britain and Germany had functioning systems. In Great Britain it was called RDF, Range and Direction Finding, while in Germany the name ''Funkmessgerät'' (radio measuring device) was used. By the time of the Battle of Britain in mid-1940, the Royal Air Force (RAF) had fully integrated RDF as part of the national air defence. By contrast, The German ''Funkmessgerät'', was neglected, partly due to Adolf Hitler's prejudice against defensive measures, and failings by the Luftwaffe in coherently incorporating the new technology. Although the technology was first demonstrated in the United States during December 1934,〔Page, Robert Moris; ''The Origin of Radar'', Anchor Books, 1962, p. 66〕 it was only when war became likely that the U.S. recognized the potential of the new technology, and began development of ship- and land-based systems. The first of these were fielded by the U.S. Navy in early 1940, and a year later by the U.S. Army. The acronym RADAR (for RAdio Detection And Ranging) was coined by the U.S. Navy in 1940, and the term "radar" became widely used. While the benefits of operating in the microwave portion of the radio spectrum were known, transmitters for generating microwave signals of sufficient power were unavailable; thus, all early radar systems operated at lower frequencies (e.g., HF or VHF). In February 1940, Great Britain developed the resonant-cavity magnetron, capable of producing microwave power in the kilowatt range, opening the path to second-generation radar systems.〔Megaw, Eric C. S.; "The High-Power Magnetron: A Review of Early Developments", ''J. of the IEE'', vol. 93, p. 928, 1946〕 After the Fall of France, it was realised in Great Britain that the manufacturing capabilities of the United States were vital to success in the war; thus, although America was not yet a belligerent, Prime Minister Winston Churchill directed that the technology secrets of Great Britain be shared in exchange for the needed capabilities. In the summer of 1940, the Tizard Mission visited the United States. The cavity magnetron was demonstrated to Americans at RCA, Bell Labs, etc. It was 100 times more powerful than anything they had seen. Bell Labs was able to duplicate the performance, and the Radiation Laboratory at MIT was established to develop microwave radars. It was later described by noted Historian James Phinney Baxter III as "The most valuable cargo ever brought to our shores".〔James Phinney Baxter III (Official Historian of the Office of Scientific Research and Development), ''Scientists Against Time'' (Boston: Little, Brown, and Co., 1946), page 142.〕〔Zimmerman, David; ''Top Secret Exchange: The Tizard Mission and the Scientific War'', McGill-Queens Univ. Press, 1996〕 In addition to Great Britain, Germany, and the United States, wartime radars were also developed and used by the Soviet Union and Japan, as well as the technically advanced Commonwealth Nations Australia, Canada, New Zealand, and South Africa. ==United Kingdom== Research leading to RDF technology in the United Kingdom was begun by Sir Henry Tizard's Aeronautical Research Committee in early 1935, responding to the urgent need to counter German bomber attacks. Robert A. Watson-Watt at the Radio Research Station, Slough, was asked to investigate a radio-based "death ray". In response, Watson-Watt and his scientific assistant, Arnold F. Wilkins, replied that it might be more practical to use radio to detect and track enemy aircraft. On February 26, 1935, a preliminary test, commonly called the Daventry Experiment, showed that radio signals reflected from an aircraft could be detected. Research funds were quickly allocated, and a development project was started in great secrecy on the Orford Ness Peninsula in Suffolk. E. G. Bowen was responsible for developing the pulsed transmitter. On June 17, 1935, the research apparatus successfully detected an aircraft at a distance of 17 miles. In August, A. P. Rowe, representing the Tizard Committee, suggested the technology be code-named RDF, meaning Range and Direction Finding. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Radar in World War II」の詳細全文を読む スポンサード リンク
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