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The Info List - AN/FPS-20





The AN/FPS-20 was a widely used L band
L band
early warning and ground-controlled interception radar system used by the United States Air Force Air Defense Command, the Pinetree Line
Pinetree Line
in Canada, and a variety of other users. The design started life as the Bendix AN/FPS-3 in 1950, was upgraded to the FPS-20, then spawned over a dozen different variants as additional upgrades were applied. The FPS-20 formed the backbone of the US air defense network through the early Cold War
Cold War
with over 200 units deployed. Most FPS-20 sites were replaced by modern equipment in the late 1960s, although a number were turned over to the FAA, modified for air traffic control use, and became ARSR-60s. The first AN/FPS-3
AN/FPS-3
arrived in December 1950, slated for installation at Eniwetok Atoll
Eniwetok Atoll
to control aircraft involved in the atomic bomb tests of early 1951.[1] Over the next few years, 48 FPS-3s were installed to replace older systems in the Lashup Radar Network. The FPS-3 and was also produced as the AN/MPS-7, a mobile version.[2] According to Winkler, the FPS-3 design was developed from the earlier CPS-5 design by Bell Labs
Bell Labs
and General Electric.[N 1] The system used two 5J26 magnetrons at 750 kW peak power, operating at 1300 MHz a 400 Hz pulse repetition frequency (prf) and 2 microsecond pulse width.[3] The antenna was driven at three fixed speeds of 3.3, 5 or 10 RPM, normally operating at 5. Many of the operating modules were mounted on the rotating platform, with the output signals fed via slip rings to amplifiers and displays at the base of the unit. The FPS-3 was limited to about 55,000 feet (17 km) altitude, which was seen as a limitation in light of new jet-powered bombers known to be in development in the USSR. This led to the development of the AN/GPA-27 add-on unit, increasing the altitude to 65,000 feet (20 km).[N 2] Installations began in 1956.[2][N 3] New-build units from Bendix with this equipment pre-installed became the AN/FPS-20 in 1957.[N 4] Otherwise similar units with an antenna from General Electric
General Electric
were known as the AN/FPS-20B. The slotted-waveguide antenna pictured above the AN/FPS-20 is for the associated IFF system.[4] The FPS-20s were simple pulse-radar systems and subject to jamming using basic techniques. This led to a second series of upgrades to provide anti-jamming capabilities starting in 1959. Among these were the GPA-102 (MK-448) which turned an FPS-20 into an FPS-64 and a FPS-20A to an FPS-66, and the GPA-103 (MK-447) which turned a FPS-20 into an FPS-65 and the FPS-20A into an FPS-67.[5] Similar upgrades using a Canadian OA-4831 system produced the AN/FPS-87 and AN/FPS-87A. The BADGE 412-L upgrade of the FPS-20A created the AN/FPS-82. A more major update was the MK-747, which added 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. Canadian AN/FPS-87s were also converted, becoming AN/FPS-93 and 93A. These units were used with the SAGE system.[6] The FPS-20 was widely used in Japan. They produced their own series of modifications, including a tunnel diode based amplifier and a separate receiver for the Airborne Instruments Laboratories system, producing the AN/FPS-20/20A JAPAN, or -J. The Indian Air Force used the FPS-20 with a new digital moving target indicator (MTI) system from Bendix to create the AN/FPS-100 and 100A. These systems were known as the "Blue Pearl", or Bendix Radar Processor BRP-150. These were remanufactured units with a new antenna, and included a new low-noise front-end amplifier. General Dynamics later produced a similar digital MTI system, the AN/FPS-113.

Contents

1 Notes 2 References

2.1 Citations 2.2 Bibliography

Notes[edit]

^ radomes.org disputes the link with the CPS-5, which had a somewhat different antenna as can be seen in the photographs in Winkler's work. This confusion may be due to the language in Bacque, which refers to "newly developed AN/FPS-3
AN/FPS-3
long-range radar set". ^ The GPA-27 may be the slotted waveguide mounted on the top of the main antenna seen in images of the FPS-20. However, some images show this on radars labeled FPS-3, although this may be before they were renamed. ^ Winkler refers to upgraded units as FPS-3B on page 76, but other sources agree with his own page 33 that these were actually called FPS-3A. ^ Winkler does not mention this directly, but notes on page 77 that -3A units were also renamed FPS-20 when receiving updates.

References[edit] Citations[edit]

^ Bacque 1990. ^ a b Winkler 1997, p. 76. ^ Radar Types ^ A high-resolution Slotted-waveguide IFF antenna for the AN/FPS-3 radar by J.Y. Wong 1957 NRC Canada. ^ Winkler 1997, p. 40. ^ Winkler 1997, pp. 77–78.

Bibliography[edit]

Bacque, Cramer (October 1990). History of the BFEC.  Winkler, David F. (June 1997). Searching the skies: the legacy of the United States Cold War
Cold War
defense radar program (PDF). Headquarters Air Combat Command. 

Further reading

AN/FPS-3, 3A, 3B; MPS-7, radomes.org AN/FPS-20, 20A, 20B, radomes.org AN/FPS-3
AN/FPS-3
Modification History Tree, radomes.org AN/FPS-20 @ fas.org

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Aerospace Defense Command
Aerospace Defense Command
(ADC)

Bases

CONUS

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Overseas

Ernest Harmon Frobisher Bay Goose Bay Keflavik McAndrew Pepperrell Thule

Stations

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Overseas

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Air Defense units

Forces

Central Air Defense Eastern Air Defense Iceland Western Air Defense First Fourth Tenth Fourteenth

Air Divisions

8th 9th 20th 21st 23d 24th 25th 26th 27th 28th 29th 30th 31st 32d 33d 34th 35th 36th 37th 58th 64th 73d 85th

Sectors

Albuquerque Bangor Boston Chicago Detroit Duluth Goose Grand Forks Great Falls Kansas City Los Angeles Minot Montgomery New York Oklahoma City Phoenix Portland Reno Sault Sainte Marie San Francisco Seattle Sioux City Spokane Stewart Syracuse Washington

Wings

Fighter 1st 4th 23d 32d 33d 50th 52d 56th 78th 81st 325th 328th 507th

Detection and Control 71st 73d 551st 552d

Air Defense 46th 4620th 4621st 4622d 4624th 4625th 4627th 4628th 4683d 4700th 4702d 4703d 4704th 4705th 4706th 4707th 4708th 4709th 4710th 4711th 4750th 4751st 4752d 4756th 4780th

Groups

Fighter 1st 4th 14th 15th 23d 32d 33d 50th 52d 53d 54th 56th 57th 78th 79th 81st 82d 84th 325th 326th 327th 328th 329th 337th 343d 355th 408th 412th 414th 473d 475th 476th 478th 507th

Air Defense 10th 500th 501st 502d 503d 514th 515th 516th 517th 518th 519th 520th 521st 525th 527th 528th 529th 530th 533d 534th 564th 566th 567th 568th 575th 637th 665th 678th 692d 701st 751st 762d 765th 778th 780th 827th 858th 4606th 4620th 4676th 4700th 4721st 4722d 4727th 4728th 4729th 4730th 4731st 4732d 4733d 4734th 4735th 4750th 4756th

Aircraft Control & Warning 503d 505th 540th 541st 542d 543d 544th 545th 546th 563d 564th 565th 566th

Squadrons

Aerospace Defense Command
Aerospace Defense Command
Fighter Squadrons Aircraft Control and Warning Squadrons

Major weapon systems

Electronic

TB-29 EB-57 EC-121

Fighters

Propellor: F-47 F-51 P-61 F-82

Subsonic Jet: P-80 F-84 F-86 F-89 F-94

Supersonic Jet: F-101 F-102 F-104 F-106

Missiles

AIM-4 AIM-26 AIR-2 CIM-10

Ships

Guardian Interceptor Interdictor Interpreter Investigator Locator Lookout Outpost Pickett Protector Scanner Searcher Skywatcher Tracer Watchman Vigil

Texas Towers

Texas Tower 2 Texas Tower 3 Texas Tower 4

Miscellaneous

Air Defense Command Emblem Gallery (on Wikimedia Commons) General Surveillance Radar Stations

v t e

US Air Force
US Air Force
Ground-based search radars

AN/FPS-3

AN/FPS-4 AN/FPS-5 AN/FPS-6 AN/FPS-7 AN/FPS-8 AN/FPS-10 AN/FPS-14 AN/FPS-16 AN/FPS-17 AN-FPS-18 AN/FPS-19 AN-FPS-20 AN/FPS-23 AN/FPS-24 AN/FPS-26 AN/FPS-27 AN/FPS-30 AN/FPS-35 AN/FPS-41 AN/FPS-49 AN/FPS-49A AN/FPS-50 AN/FPS-65 AN/FPS-77 AN/FPS-85 AN/FPS-92 AN/FPS-95 AN/FPS-100 AN/FPS-107 AN/FPS-108 AN/FPS-113 AN/FPS-115 AN/FPS-117 AN/FPS-120 AN/FPS-123(V3) AN/FPS-123(V7) AN/FPS-124 AN/FPS-126 AN/FPS-12

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