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FPS-18 Short Range Gap Filler Radar Set - A Short Range Gap Filler Radar set built by Bendix Radio Division of Bendix Aviation Corporation. Deployed during the 1950s and early 1960s in unattended gap-filler radar sites to fill in gaps in the long range radar coverage. Used in the SAGE System to directly send target data to a SAGE direction center. The radar antenna was mounted on a three legged tower and sometimes covered with a radome.

Typical FPS-18 Gap Filler Radar Site

The radar set itself was contained in a small two room "L" shaped building with the smaller room containing up to three backup power generators and the larger room containing the dual channel radar set. That room also contained the FST-1 Coordinate Data Transmitter that digitized the radar data and transmitted target data to the direction center via phone lines. Also in that room was the FSW-1 Control Monitor Set that enabled remote control from the radar site of power switching and channel changes on the dual channel equipment. The FSW-1 also monitored up to 30 functions on the site and could control up to 20 functions remotely.

FPS-18 Gap Filler Radar

FPS-18 Gap Filler Radar
Element Value Notes
Nomenclature FPS-18
Variants FPS-18A
Manufacturer Bendix Radio Division of Bendix Aviation Corporation
Budd Lewyt Company
Type Gap Filler
Number Made 100~
Frequency 2700 - 2900 Tunable
PRF 1200 pps
Pulse Width 1 us
Rotation Speed 5.33 rpm
Power 1 mw V87-B or V87-C klystron
Range 35 - 50 nmi Short Range
Altitude 17,000 feet
Introduced 1950s
Stock Numbers 5840-505-0435 FPS-18
5840-646-9897 FPS-18A

FPS-18 Components (edit list)
Component Model Quantity Height Width Deep Weight Notes
Antenna Group OA-897A/FPS-14 1 2,918 lb
Transmitter Group OA-1140/FPS-18 2 84" 56" 35.5" 1,805 lb
Power Supply PP-1497/FPS-18 2 84" 44" 34.125" 1,745 lb
Electron Tube Liquid Cooler MX-2010/FPS-18 2 46" 30" 56 lb
Receiver Group QA-1231/FPS-18 2 84" 40" 24" 844 lb
Indicator Group QA-1339/FPS-18 1 40" 18.5" 30.5" 213 lb
Control Monitor C-2097/FPS-18 1 53.125" 10" 27" 485 lb
Motor Generator PU-366/FPS-18 1 2,000 lb
Voltage Regulator CN-385/FPS-18 2 40.5" 24" 20.8" 495 lb
Directional Coupler CU-453/FPS-14 2 7.75" 5.25" 24.5" 32 lb
Waveguide Switch SA-436/FPS-14 1 11.75" 13.25" 13.25" 34 lb
Dummy Load DA-114/FPS-14 1 5" 6.25" 31.5" 31 lb
Mobile Test Cart FN-83/FPS-14 2 24" 38.5" 32" 62 lb

See Also:


  • Winkler, David F., Searching the Skies: the Legacy of the United States Cold War Defense Radar Program, USAF Hq Air Combat Command, 1997, 192 pages, Pdf
  • MIL-HDBK-162A, 15 Dec 1965.


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