Radar

A Thumbnail History of Electronics

VI. Radar

In the period before World War II, all the major powers were developing radio location systems. The British concentrated on aircraft detection and location while the Germans developed aircraft navigation systems. These devices operated at meter wave lengths. The invention of the multicavity magnetron by Randall and Root in Britain in 1939 provided the impetus to the development of the centimeter wavelength systems required for modern radar. The disclosure of the device to the U.S. in 1940 was followed by the founding of the Radiation Laboratory at MIT. The Radiation Laboratory technical staff grew to more than 1300 engineers and scientists, including ten future Nobel Laureates, and developed more than one hundred models of radar, including early warning systems, anti-aircraft gun-laying radars, anti-submarine radars, ground approach systems, and bomber targeting radars. Other radars were developed at Bell Labs and elsewhere. Nearly one million radar sets were produced in the U.S. as the war progressed! The Germans and the Japanese also produced a variety of radar systems. However, the Germans never produced the short wavelength systems available to the Allies and were caught in a losing game of technical catch-up. The Japanese, who had independently invented the magnetron, were hampered by bureaucratic entanglements, military secrecy and personnel shortages as engineers were regardlessly drafted into the army.
Robert Alexander Watson-Watt (1892-1973), a descendant of James Watt, received a degree in Electrical Engineering from the University of St. Andrews, Scotland and in 1915 began a career in the British civil service, He patented his first radio location device, a device for locating atmospheric discharges, in 1919. In 1935, he received his eleventh radio-location patent, a device for detecting and locating an approaching aircraft. In the following years he was the leader of the intensive development of aircraft radio-location, the secret weapon of the Battle of Britain. In 1937, before the war began, Watson-Watt and his wife undertook the dangerous task of traveling disguised as ordinary tourists through Germany, searching for signs of German radar stations.
Alfred Lee Loomis (1887-1975), a graduate of Yale and Harvard Law School, was called "the last of the great amateurs of science". Loomis made a fortune on Wall Street and used his wealth to play host at his estate to famous physicists and to finance a private electronics laboratory; he had already built a working low-power CW radar for aircraft detection when the British brought the magnetron to the U.S. in 1940. In the following months, Loomis helped found the Radiation Laboratory and became head of the Microwave Committee of the National Defense Research Committee. In 1940, Loomis conceived the idea of a precision long-range radio navigation system, Loran. By 1942, the first Loran system, operating at 1.95 MHz, was operating along the East Coast and was used to direct surface vehicles the location of aircraft attacking submarines. Loomis is also credited for conceiving the conical scan system for automatic radar tracking of targets.
Isador Isaac Rabi (1898-1988) was brought to the United States at age three by his parents to escape the poverty of Eastern Europe. His father labored in the sweatshops of New York City and then opened a grocery store in Brooklyn to escape the tenements of Manhattan. Rabi earned his degrees at Columbia and Cornell, and became a professor of Physics at Columbia in 1937. In 1940, Rabi took leave from Columbia to become director of research at the newly-formed MIT Radiation Laboratory. Rabi, who hated the Nazis, would respond to any proposed project by asking, "How many Germans will it kill?" The projects under his immediate direction involved increasing the power and frequency of the magnetron oscillators. In 1944 He was awarded the Nobel Prize for his (1937) invention of the magnetic resonance method for determining atomic spectra.
Luis Walter Alvarez (1911-1988) was one of the most versatile of the physicists who worked at the Radiation Laboratory. Alvarez, who was of Irish-Spanish descent, was the son of a prominent Mayo Clinic physician. He began his career as a nuclear physicist at Berkeley in 1937 and made a number of fundamental discoveries. In 1940 he joined the Radiation Laboratory staff and invented the Ground-Controlled Approach radar for aircraft landing, a microwave early warning radar, and a precision high-altitude bombing radar. In 1944 he transferred to the Manhattan project, where he invented the implosion system for initiating atomic explosions. He was awarded the Nobel prize in 1968 for his development of the hydrogen bubble chamber and the discovery of many subatomic particles. In 1980, he and his son, a geologist, co-authored the theory of the catastrophic annihilation of the dinosaurs as the result of a massive meteorite impact.
Edward Mills Purcell (1912-1997) grew up in a small Illinois town where his father managed the local office of the telephone company. Purcell obtained a BSEE at Purdue and then turned to Physics. He was an instructor at Harvard until he joined the newly formed Radiation Laboratory where he led a group developing one centimeter wavelength radar systems. It was discovered that these systems were limited by absorption by atmospheric water vapor. This work put him on the track to his 1945 discovery of nuclear magnetic resonance in liquids and solids, the basis for NMR medical imaging. In 1952 he was awarded the Nobel prize for this discovery.
Robert Henry Dicke (1916-1997) delayed his arrival at the Radiation Laboratory in order to finish his dissertation in Physics at the University of Rochester. Dicke’s inventiveness led to 35 radar-related patents. He invented mono-pulse and coherent-pulse radar and devices such as the magic-T waveguide junction. To measure water vapor absorption at centimeter wavelengths, Dicke invented a radiometer which became the standard detector for radio astronomy. Dicke later became a professor at Princeton. He challenged Einstein’s general theory of relativity and conducted a series of gravity experiments which were eventually unsuccessful. He also correctly theorized that a microwave echo from the Big Bang that created the universe could be detected.

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