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Description of the radar set, tactical-technical characteristics

Figure 1: Bendix AN/FPS-20 Radar

frequency: 1 280 … 1 350 MHz
pulse repetition time (PRT): 2 858 µs
pulse repetition frequency (PRF): 350 Hz
pulsewidth (τ): 2 µs
receiving time:
dead time:
peak power: 2 … 2.5 MW
average power: 4.35 … 6 KW
instrumented range: 231 NM (≙ 428 km)
range resolution: 1000 Yard
beamwidth: 1.3°
hits per scan:
antenna rotation: 3.3, 5 or 10 rpm


AN/FPS-20 was a widely used L-band early warning and ground-controlled interception radar system, developed by Bendix orporation. The radar family started with the AN/FPS-3 in 1950, used a transmitter with two magnetrons.

The production of AN/FPS-20 began in 1956 with a dual-channel liquid-cooled klystron transmitter. Each receiver used the “Dicke Fix”- processing. The antenna was equipped with a polarizer and could work alternating in circular or linear horizontal polarization.

Later updates (including anti-jamming opportunities mostly) led to the designations AN/FPS-64, AN/FPS-65, AN/FPS-66, AN/FPS-67, AN/FPS-91, AN/FPS-93, AN/FPS-100, AN/FPS-113 and AN/GPS-4. The Canadian vwesion got the designator AN/FPS-508.

Radar Redesignations
Original System + Upgrade= New System
AN/FPS-20 + AN/GPA-102 = AN/FPS-64
AN/FPS-20 + AN/GPA-103 = AN/FPS-65
AN/FPS-20A + AN/GPA-102 = AN/FPS-66
AN/FPS-20A + AN/GPA-103 = AN/FPS-67
AN/FPS-20 + OA-7091/FPS  = AN/FPS-100

Similar upgrades using a Canadian OA-4831 system produced the AN/FPS-87 and AN/FPS-87A. A more major update was the adding of a new antenna from Raytheon, the Diplex Gating Unit (DGU), a bandpass filter and other modifications, to produce the AN/FPS-91 and 91A. The similar MK-748 applied to the -60 series resulted in the AN/FPS-64A, -65A, -66A and -67A. The radar AN/FPS-66A was also used by the FAA as en-route radar and got the designator ARSR-66. Canadian AN/FPS-87s were also converted, becoming AN/FPS-93 and 93A.

Picture gallery of AN/FPS-20

Figure 2: The antenna of the AN/FPS-508 as static display in North Bay, Ontario.