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AN/ALR-20

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AN/ALR-20(A) is an airborne wideband tuned radio frequency receiver providing a panoramic display of Radio Frequency (RF) spectrum on US Air Force B-52 Stratofortress aircraft. As a stand-alone system, it is used by the Electronics Warfare Officer (EWO) to evaluate and determine various classifications of threats to the aircraft,[1] identifying various signals including search, acquisition, and tracking radars as well as communications. Because it allows a broad view of the RF spectrum, its situational awareness also provides for analysis of the efficacy of jamming techniques employed by the EWO using other systems. First manufactured in the late 1960s, the system is a passive Electronic Support Measures (ESM) tuned radio frequency receiver.[2][3] It is the primary tool used by the EWO to evaluate threats.[4]

History

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First developed in the early 1960s,[3][5] the ALR-20 began appearing on B-52D bombers (before 1967)[6] and B-52Gs in 1967-1969.[7][8] The ALR-20 did not undergo any significant upgrades or design changes until the 1980s. In the 80s, solid-state components were added to the system's tuners upgrading older tube-based technology.

Until the late 1990s, the ALR-20's panoramic receiver display utilized Cathode-Ray Tube (CRT) technology. At the beginning of the 1990s, the outdated panoramic display (using old cathode ray tube technology) needed replacement due to the existing display becoming unsupportable. This replacement was delivered in the late 1990s. At that time, tuners and the power supply were determined to also need replacement for the same reasons.[3] Today, deployed on B-52H bombers, the system still provides the EWO a display of six different RF bands, allowing for detection and identification of threat signals.[3][9]

Into the early 2000s, it was determined the system was "becoming unsupportable due to vanishing vendors and obsolete technology".[5] Under the B-52 Situational Awareness Defensive Improvement (SADI) program, the ALR-20 is expected to be replaced with a defensive system upgrade. The upgrade is expected to create up to thirty-fold improvements in reliability.[10] Efforts to replace the ALR-20 continued into the mid-2000s, while some work was done to continue maintaining line replaceable units (LRUs). In 1999, ninety-one LRU-1s, fifty-four LRU-3s, thirty-six LRU-8s, eighty-three LRU-9s were repaired at a total cost of over $315,000.[11] According to the Air Force's Fiscal Year (FY) 2004/2005 budget estimates, SADI would cost just over $70.9 million.[5]

Electronic Warfare Officers undergo extensive training concerning the ALR-20 panoramic system.[12]

Technical description

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Features

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AN/ALR20A Panoramic Display - Illustrated Parts Breakdown

The ALR-20's panoramic display is the EWO's primary source for analysis of potential threats through a very wide part of the electromagnetic spectrum.[13] The early cathode-ray tube for the display (seen in the image to the right) had an orange tint displaying six different horizontal lines that represented a part of the spectrum. The signals displayed on those lines may be quickly analyzed allowing the EWO to bring the proper countermeasures for multiple different threats at once.[13][14]

Components

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  • Receiving Set Controller - LRU-1[11]
  • Panoramic Display
  • Power Supply - LRU-3[11]
  • Radio Frequency Tuner - LRU-8[11]
  • Radio Frequency Tuner - LRU-9[11]

Variants

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  • AN/ALR-20
  • AN/ALR-20A

See also

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References

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  1. ^ "Repair of AN/ALR-20 Panoramic Indicator", GovTribe, July 9, 2018, retrieved July 21, 2024
  2. ^ "AN/ALR-20 (Panoramic Receiver Set, Phase V ECM Fit)", CMANO-DB, July 9, 2018, retrieved July 21, 2024
  3. ^ a b c d Pike, John (April 22, 2000), "AN/ALR-20", Federation of American Scientists - Military Analysis Network, retrieved July 21, 2024
  4. ^ Goebel, Greg (June 1, 2024), "3.0 The B-52 In The Modern Era", AirVectors, retrieved August 17, 2024, A "Phase VI ECM Defensive Avionics Systems" upgrade, codenamed "Rivet Ace", was begun more or less near the end of the EVS upgrade. It included a comprehensive update of countermeasures systems for the B-52G and B-52H, including: An AN/ALR-20A wideband countermeasures receiving set, with antennas littered all over the aircraft. The "20 Scope" is the primary tool for detecting and analyzing threats.
  5. ^ a b c Department of the Air Force Fiscal Year 2004/2005 Biennial Budget Estimates (PDF), February 2003, p. 1178, retrieved August 17, 2024, ...replacing the AN/ALR-20 Panoramic Receiver System. The present AN/ALR-20 system, designed in the 1960's, is becoming unsupportable due to vanishing vendors and obsolete technology and has extremely limited SOJ support capability.
  6. ^ Goebel, Greg (June 1, 2024), "2.0 The B-52 In The Cold War", AirVectors, The B-52D also received new upgrades to improve its combat effectiveness, most significantly with the "Rivet Rambler" program, conducted from 1967 through 1969 to provide an improved ECM suite. Rivet Rambler, more officially referred to as the "Phase V ECM Fit", fitted the B-52Ds with the following gear: An AN/ALR-20 panoramic receiving set.
  7. ^ Baugher, Joe (April 21, 2021), Boeing B-52G Stratofortress, retrieved September 13, 2024, During 1967-1969... This involved the fitting of... one AN/ALR-20 panoramic receiver set. The Phase VI ECM Defensive Avionics Systems upgrade... was started in December of 1971, but it took several years of development and testing. The equipment added as part of Phase VI consisted of an AN/ALR-20A countermeasures receiver
  8. ^ Leone, Dario (December 17, 2023), "40 Years ago the USAF retired the last B-52D, the BUFF model used to bomb North Vietnamese targets during Christmas Bombing Operation Linebacker II", Aviation Geek Club, retrieved August 17, 2024, B-52Ds were equipped with an extensive suite of electronic countermeasures during the 'Rivet Rambler' programme of 1967 to 1969... This included the addition of... the AN/ALR-20 panoramic receiving set
  9. ^ "B-52H Stratorfortress", Air Force Technology, September 6, 2024, retrieved September 13, 2024
  10. ^ Guse, Paul (September 14, 2000), Boeing Awarded Contract to Develop B-52 Defensive System Upgrade, retrieved September 13, 2024, Through the SADI program, Boeing will replace the aging ALR-20A Electronic Countermeasures Receiver System and the ALR-46 Radar Warning Receiver on the B-52 Stratofortress. These upgrades are expected to offer up to a thirty-fold improvement in system reliability.
  11. ^ a b c d e Gehrich, David L. (2004), Benefifits from Funding the MSD Engineering List: A Fiscal Year 1999 Case Study (PDF), Wright-Patterson AFB, Ohio: Air Force Institute of Technology, retrieved September 13, 2024
  12. ^ Occupational Survey Report - Electronic Warfare Systems - AFSC 2A1X7 (PDF), October 1996, retrieved September 13, 2024
  13. ^ a b Blank, Steve (March 29, 2009), The Story Behind the Secret History Part II. Getting B-52s through the Soviet Air Defense, retrieved September 14, 2024
  14. ^ Mitchell, Sid (May 29, 2019), "Iron Butterfly' – a close look at the B-52H Stratofortress during Exercise Diamond Storm 2019", Aviation Spotters Online, retrieved August 17, 2024, The AN/ALR-20 radar warning system that detects and prioritises multiple threats...
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