EARLY HISTORY OF RADAR — PAGE 321 



about 200 feet square. Reduction in directivity of antenna pattern 

 was not desired. A smaller antenna therefore meant higher fre- 

 quency. On July 22, 1936, a small radar was put in operation on 200 

 Mc. In that same month the first radar duplexer was successfully 

 tested, also on 200 Mc, enabling both transmitter and receiver to use 

 the same antenna. These two quick developments made it possible to 

 put radar on a ship for tests at sea. The first seagoing radar tests 

 were made in April 1937, on the U.S.S. Leary^ an old destroyer of the 

 Atlantic Fleet. The success of these tests led to the development of 

 the model XAF, designed for Naval service at sea. Extensive tests 

 on the U.S.S. New York in 1939 disclosed operational values beyond 

 all dreams. The XAF was made prototype for the model CXAM, 

 which was in service on 19 ships, the only U.S. Naval radar in service 

 on December 7, 1941. It made an excellent wartime record. 



This is a brief outline of the main stream in the early development 

 of radar, resting on a sequence of related events from 1922 to 1941. 

 Up to the summer of 1935 it was a single stream. At that time two 

 other streams started, both remarkably parallel to the main stream. 

 The one in England, sparked by the proposal of Watson- Watt in 

 February 1935, and conducted under the aegis of the Royal Air 

 Force, was completely independent of the American developments 

 until 1940, at which time the two countries pooled their resources. In 

 the technological trade, America gained the uniquely British cavity 

 magnetron, and Britain gained the uniquely American duplexer. The 

 trade was not as one-sided as may have been inferred in some of 

 the postwar literature. The pooled resources formed the technologi- 

 cal capital for the newly formed National Defense Research Commit- 

 tee in the superb development of microwave radar by the Radiation 

 Laboratory of the Massachusetts Institute of Technology. The other 

 stream, in the U.S. Army Signal Corps, sparked by the dynamic 

 leadership of Col. Roger B. Colton, was independent in part, but 

 received much stimulation, both competitive and cooperative, from 

 the more advanced work of the U.S. Naval Research Laboratory. It 

 is one of the most remarkable coincidences in history that the three 

 streams of radar development, operating more or less independently, 

 issued in three vital but nonoverlapping employments, each requiring 

 basically different designs. At the war's beginning the finest mobile 

 ground-based radar came from the U.S. Army Signal Corps, the 

 finest airborne radar came from the Royal Air Force, and the finest 

 Naval radar came from the U.S. Navy. 



