The AN/FRD-10 is a United States Navy circularly disposed antenna array (CDAA), 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.

[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 circular arrays.

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.

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.

For example, the antenna at NSGA Winter Harbor had problems due to frost heaving the ground and shifting the reflector screens out of alignment.

An alternative method was discovered that modified the poles to allow readjustment of the screen instead of the costly removal and replacement that had been done in the past.

Antenna arrays at Homestead, Florida and Sabana Seca, Puerto Rico were heavily damaged by Hurricanes Andrew and Georges, respectively.

[4] The AN/FRD-10 had an estimated range of 3,200 nautical miles (5,900 km) and was used to monitor and triangulate single or double hop high frequency (HF) signals between 2 and 32 MHz.

[2] The Navy also claimed over the years that the direction finding sites were used primarily for air and sea rescue operations[17][19] and Naval communications in the case of the pair of FRD-10s at Sugar Grove Station.