page_title: AN/FRD-10
section_title: Construction and Cost
hierarchical_section_title: AN/FRD-10 / Construction and Cost
caption_attribution_description: AN/FRD-10 - Figure 2-2 Plan-View of CDAA.
context_page_description: The AN/FRD-10 Circularly Disposed Antenna Array was a United States Navy circular "Wullenweber" antenna array, built at a number of locations during the cold war for high frequency radio direction finding 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. 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. As of 2015, none of the US Navy AN/FRD-10 sites are extant, but the two Canadian sites remain in service. The AN/FLR-9 was a system with a similar design and function, but operated by the US Air Force and Army.
context_section_description: In 1959, the Navy awarded a contract to ITT Federal Systems to construct a network of AN/FRD-10 systems. 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). 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. One site was short lived. NSGA Marietta, Washington closed in 1972 and reverted to a Lummi reservation. Marietta was the first FRD-10 site to shut down and operated less than 10 years.
  The 1970 estimate to construct a CDAA was just under $900,000 ($5.93 million today) with electronics at the site estimated at around $20 million ($132 million today). The system had 120 high band antennas and 40 low band antennas which had to be positioned within +/- two minutes of arc and +/- 3 inches of their intended distance from the center of the array. 160 75 ohm coaxial transmission lines were used to carry signals from the antennas had to be electrically matched to within 3/4 of a degree at 10 MHz. This task was estimated at 300 to 400 man hours to complete. There was also an extensive grounding system used at the FRD-10 sites. This included 360 ground radials made of 8 AWG wire, 150 feet (46 m) long, extending from the outer antenna ring. It also included a massive ground grid, made of 10 AWG wire bonded together to create a mesh with 2 feet (61 cm) squares. It was laid underground up to the radials in the area between the high and low antennas.
  Weather proved to be a challenge for the FRD-10 antennas. For example, the antenna at NSGA Winter Harbor had problems due to frost heaving the ground and shifting the reflector screens out of alignment. Digging up the affected poles and replacing them was costly and was estimated at around $240,000 in the late 1970s. An alternative method was discovered that modified the poles to allow readjustment of the screen instead the costly removal and replacement that had been done in the past. The arrays were also vulnerable to high winds. Antenna arrays at Homestead, Florida and Sabana Seca, Puerto Rico were heavily damaged by hurricanes Andrew and Georges, respectively.
caption: Plan view of a CDAA quadrant
exif: {}