Bendix AN/FPS-18 Radar

The AN/FPS-18 was a medium-range search radar used by the United States Air Force Air Defense Command.

This medium-range search radar was designed and built by Bendix as a SAGE system gap-filler radar to provide low-altitude coverage. Operating in the S-band at a frequency between 2700 and 2900 MHz, the AN/FPS-18 could detect at a range of 65 miles.

The system was deployed in the late 1950s and 1960s at unmanned radar facilities (called "Gap Fillers") designed to fill the low-altitude gaps between manned long-range radar stations. Gaps in coverage existed due to the curvature of the Earth, mountains, hills, valleys, rivers, and so forth.

The typical unmanned gap-filler radar annex consisted of a small L-shaped cinder-block building, with the radar equipment and the data-transmission equipment in one section and one or more diesel generators in the other section. These unmanned gap-filler sites generally had a three-legged radar tower about 85 feet tall where the AN/FPS-18 Radar was mounted inside a radome.

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-18 represents the 18th design of an Army-Navy “Fixed, Radar, Search” electronic device.