Westinghouse AN/FPS-27 Radar

The AN/FPS-27 Radar was a long-range search radar used by the United States Air Force Air Defense Command.

Westinghouse built a Frequency Diverse (FD) search radar designed to operate in the S-band from 2322 to 2670 MHz. The radar was designed to have a maximum range of 220 nmi and search to an altitude of 150,000 ft.

System problems required several modifications at the test platform located at Crystal Springs, Mississippi. Once these problems were solved, the first of twenty units in the continental United States became operational at Charleston, Maine, in 1963. The last unit was installed at Bellefontaine, Ohio, a year later. All AN/FPS-27 radars were installed at sites which had AN/FPS-6, AN/FPS-26, or AN/FPS-90 height finder radars. The 3-D functionality of the AN/FPS-27 was not available to the AN/FYQ-47 Common Digitizer for use in the Semi-Automatic Ground Environment (SAGE) system.

The 3-D functionality was possible through the use of a "vertically stacked beam" radiating feedhorn into the parabolic reflector. The received radar return was detected in a single or adjacent feedhorn which the radar receiver calculated a relative position in elevation.

In the early 1970s, AN/FPS-27 radar stations that had not been shut down received a modification (solid state receiver circuitry replacing vacuum tubes) that improved reliability and saved on maintenance costs. The upgraded radars were designated AN/FPS-27A.

Classification of radar systems
Under the Joint Electronics Type Designation System (JETDS), all U.S. military radar and tracking systems are assigned a unique identifying alphanumeric designation. The letters “AN” (for Army-Navy) are placed ahead of a three-letter code.
 * The first letter of the three-letter code denotes the type of platform hosting the electronic device, where A=Aircraft, F=Fixed (land-based), S=Ship-mounted, and T=Ground transportable.
 * The second letter indicates the type of equipment, where P=Radar (pulsed), Q=Sonar, and R=Radio.
 * The third letter indicates the function or purpose of the device, where G=Fire control, R=Receiving, S=Search, and T=Transmitting.

Thus, the AN/FPS-27 represents the 27th design of an Army-Navy “Fixed, Radar, Search” electronic device.