AN/FRD-10
The AN/FRD-10 Circularly Disposed Antenna Array (CDAA) is a United States Navy circular "Wullenweber" antenna array, built at a number of locations during the cold war for high frequency radio direction finding (HF/DF) and signals intelligence. In the Joint Electronics Type Designation System, FRD stands for fixed ground, radio, direction finding. 14 sites were originally constructed as a part of the "Classic Bullseye" program.[2][3] Two AN/FRD-10 systems were later installed in Canada. AN/FRD-10 systems were originally constructed in the early 1960s, but after the dissolution of the Soviet Union, the systems began to be shut down and demolished. The Naval Security Group operated and maintained the U.S. Navy AN/FRD-10 systems. The system had several nicknames including Fred-10 and Elephant or Dinosaur cages.[4] As of 2015, none of the US Navy AN/FRD-10 sites are extant, but the two Canadian sites remain in service.[citation needed] The AN/FLR-9 was a system with a similar design and function, but operated by the US Air Force and Army.
The program to install and operate the radio direction finding network was known as Bullseye, Clarinet Bullseye and Classic Bullseye at various points over its life cycle.[5] The word Classic was likely added later when permanently assigned "first words" were created for two-word nicknames. Classic was the word used to designate programs related to the Naval Security Group and Clarinet was used for programs related to the Chief of Naval Operations.[6][7]
Classic Bullseye was also related to the Centerboard and Flaghoist programs.[8] Centerboard was a network for processing HF/DF information.[9] The security classification guide that covered all three programs was cancelled in January 2009.[10][11] Later, the programs Unitary DF and Crosshair sought to unify the military's HF direction finding information into a single data collection network.[12] Crosshair, an HF/DF geolocation network, is apparently still in use c. 2015, employing small fixed or mobile HF/DF systems instead of large Wullenweber arrays.[13]
The United States Naval Research Laboratory (NRL) led development of the technology that was used in the AN/FRD-10. Three developments were critical to the FRD-10, the ability to record portions of the frequency spectrum for future analysis, the Circularly Disposed Antenna Array (CDAA) and the computer control system that allowed rapid triangulation across multiple sites.[14] NRL funded research at a test site built in 1955 by the University of Illinois at the Bondville Road Field Station in Scott Township, Champaign County, Illinois, south of Bondville, Illinois.[15] The AN/FRD-10 antenna was a scaled-up version of the NRL prototype antenna array.[12]
In 1959, the Navy awarded a contract to ITT Federal Systems to construct a network of AN/FRD-10 systems.[16] The first AN/FRD-10 to be constructed was at NSGA Hanza in Okinawa, but future FRD-10 sites had different antenna dimensions. The High band reflector was reduced from 120 ft to 90 ft in later sites. Additionally, the outer high band antenna ring at Hanza was 311 feet (95 m) from the center with later sites being around 435 feet (133 m).[1] For the remaining sites, the outer antenna elements were spaced every 3 degrees around the circle and the outer reflector was 24.3 feet (7.4 m) tall. The inner antenna elements were spaced every 9 degrees and the inner reflector was 90 feet (27 m) tall.[1] One site was short lived. NSGA Marietta, Washington closed in 1972 and reverted to a Lummi reservation.[17] Marietta was the first FRD-10 site to shut down and operated less than 10 years.
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