Card Index of Radar Sets - Ancient Radars

AN/CPS-4 height-finding radar

AN/CPS-4 “Beaver Tail” was a medium range S-Band nodding height-finding radar developed by MIT’s Radiation Laboratory used by the United States Air Force Air Defense Command. The radar was designed to be used in conjunction with the SCR-270 and SCR-271 search sets.

The CPS-4 required six operators. This S-band radar could detect targets at a distance of ninety miles. It showed these targets on an RHI-scope. The AN/CPS-4 antenna was horn fed with a reflector 20 x 5 ft shaped as an elliptical section of a paraboloid. The antenna gave a beam 1.2° wide in the vertical plane, and to pick up the targets in altitude this was raised and lowered 25 cycles per minute by nodding the antenna structure between −2° and 32°. The radars accuracy was 1000 ft in absolute altitude and 500 ft in relative altitude at 45 miles range, preferably 90 miles.[1] This radar was often paired with the AN/FPS-3 search radar during the early 1950s at permanent network radar sites.

The first production model AN/CPS-4 came out in June 1945. The AN/CPS-4 was installed e.g. in der Keesler AFB, in US Omaha Air Force Station (AFS) and Belleville AFS,[2] as well as in Germany on the Erbeskopf-Site. The AN/CPS-4 was also used in meteorology, to explore the structure of the “Bright Band”.[3]