The SCR-268 (short for Set, Complete, Radio no. 268) was the United States Army's first radar system. Introduced in 1940, it was developed to provide accurate aiming information for antiaircraft artillery and was also used for gun laying systems and directing searchlights against aircraft. The radar was widely utilized by both Army and Marine Corps air defense and early warning units during World War II. By the end of World War II the system was already considered out of date, having been replaced by the much smaller and more accurate SCR-584 microwave-based system.
Development The Signal Corps had been experimenting with some radar concepts as early as the late 1920s, under the direction of Colonel William R. Blair, director of the Signal Corps Laboratories at Fort Monmouth, New Jersey. While most of the Corps' efforts revolved around infra-red detection systems (a popular idea at the time), as well as a newer generation of sound detectors, they also maintained a small program of research on microwave radars based on the "beat principle", in which an aircraft would cause two signals to interfere. Low generator efficiency and a lack of ranging capability made these efforts impractical. In 1935 one of Blair's recent arrivals, Roger B. Colton, convinced him to send an engineer to investigate the US Navy's CXAM radar project after the bureau of Standards requested a proposal for radio detection of aircraft. The navy's system traced its development from experiments conducted by Albert H. Taylor and Leo C. Young at the United States Naval Research Laboratory in the early 1920s. William D. Hershberger duly went to see what they had, and returned an extremely positive report. Gaining the support of James B. Allison, the Chief Signal Officer, they managed to gather a small amount of funding and "stole" some more from other projects. By December 1936 they had a working 3 meter prototype, which they continued to work on and improve. In November 1938 they were able to show the 1.5 meter prototype in a convincing demonstration for Hap Arnold. After failing to find their target Martin B-10 bomber where it was supposed to be, they started "hunting" for it and found it 10 miles off course. The radar fed pointing data to a team operating a searchlight, and when it was turned on the bomber was seen to be centered in the beam. It was later learned that the target had been blown off course, making the demonstration all the more impressive. Development of this system was slowed to some degree when a long range early-warning radar became a higher priority and parts of the prototype were salvaged for the SCR-270 they were building. Nevertheless, the system entered production at Western Electric about the same time as the -270 in 1939. The radar entered service in 1940, and about 3100 were produced by the end of the war. In 1944, the SCR-268 radar unit was beginning to be replaced by the SCR-584 radar. The SCR-268 was able to acquire and direct guns, or searchlights, on a target with a single piece of equipment.
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