SCR-270/271

The United States Army Signal Corps started developing radar as early as 1930. In 1935, tests on microwave propagation tests using Hollmann built valves, RCA magnetron operating at 9 cm, RCA acorn valves were performed. In 1937 the test radar unit was demonstrated. Based on this test unit, in 1940, the SCR-270 became available for coastal defense and it was first deployed in Panama in the Fall of 1940 as an early warning for the Air Corps, Pursuit Squadron. This unit operated on a frequency of 205 MHz (l=1.5m) and had a range of 23 miles, had an angular accuracy of 1 deg. Eighteen units were built by the Army Signal Corps Laboratory for training purposes. The Signal Corps awarded a contract to Westinghouse for production of the early-warning radars in August 1940. By June of 1941 a total of 85 sets had been delivered by Western Electric. By the end of 1941 over a hundred sets had been delivered. A total of 794 were produced between 1939 and 1944.

The SCR-270 was a "mobile" long range, early warning air defence search radar and it made use of a 12 inch PPI.

The SCR-271 was a "fixed version" of the SCR-270. It was used for aircraft detection and air defense of American and Canadian coastal areas. The SCR-271 also made use of a 12 inch PPI.

Both the SCR-270 and the SCR-271 operated at 3 meters/100 MHz, with a peak power of 100 kW, a pulse width from 10 to 25 microseconds, and a PRF of 621 Hz. They lacked lobe switching.