[masraum]

Originally Posted by F150 FX4

This was also in Alaska, I drove by it. I was told it was for low speed through the earth contact with our ballistic subs.

I'm guessing you are talking about Elmendorf. There was another one in Adak, AK, but I don't think anyone was ever just driving by Adak, LOL.

I'd heard the same thing at one point, but I think those antenna arrays are primarily for receiving and locating high frequency, not low frequency.

Per wikipedia

The AN/FLR-9 is a type of very large circular "Wullenweber" antenna array, built at eight locations during the cold war for HF/DF direction finding of high priority targets. The worldwide network, known collectively as "Iron Horse", could locate HF communications almost anywhere on Earth. Because of the exceptionally large size of its outer reflecting screen (1056 vertical steel wires supported by 96 120-foot (37 m) towers), the FLR-9 was commonly referred to by the nickname "Elephant Cage." Constructed in the early to mid 1960s, in May 2016 the last operational FLR-9 at Joint Base Elmendorf-Richardson in Alaska was decommissioned.

The antenna array is composed of three concentric rings of antenna elements. Each ring of elements receives RF signals for an assigned portion of the 1.5 to 30-MHz radio spectrum. The outer ring normally covers the 2 to 6-MHz range (band A), but also provides reduced coverage down to 1.5 MHz. The center ring covers the 6 to 18-MHz range (band B) and the inner ring covers the 18 to 30-MHz range (band C). Band A contains 48 sleeve monopole elements spaced 78.4 feet (23.9 m) apart (7.5 degrees). Band B contains 96 sleeve monopole elements spaced 37.5 feet (11.43 m) apart (3.75 degrees). Band C contains 48 antenna elements mounted on wooden structures placed in a circle around the central building. Bands A and B elements are vertically polarized. Band C elements consist of two horizontally polarized dipole antenna subelements electrically tied together, and positioned one above the other.

The array is centered on a ground screen 1,443 feet (439.8 m) in diameter. The arrangement permits accurate direction finding of signals from up to 4000 nautical miles (7408 km) away.
AN/FLR-9 antenna array at Misawa Air Base c. 1980

FLR-9s were constructed at the following places:

USASA Field Station Augsburg (Gablingen Kaserne), Germany
Chicksands, England
Clark AB, Philippines
Joint Base Elmendorf-Richardson, Alaska, USA (formerly designated as Elmendorf AFB)
Karamursel, Turkey
7th Radio Research Field Station/Ramasun Station, Udon Thani Province, Thailand
Misawa AB, Japan, built 1963 to 1965, demolished beginning in 2014.
San Vito dei Normanni Air Station, Italy (near Brindisi, Italy)

Advances in technology have made the FLR-9 obsolete. In 1997, the FLR-9 at the former Clark AB in the Philippines was converted into a 35,000-seat fabric-covered amphitheatre. In early May 2002, systematic dismantling of the FLR-9 at San Vito began, and it was totally deconstructed by the end of that month. Although the markings of where the array stood remain in the ground, the structure is completely gone.

Demolition of the FLR-9 at Misawa began in October 2014.

A decommissioning ceremony for the last active FLR-9, at Joint Base Elmendorf-Richardson, was held on May 25, 2016.

There were other similar antenna arrays that were "AN/FRD10" that were basically the same. We could have ended up stationed at those as well.

Dad was stationed in Misawa twice, was in Pensacola the first time as a student, and the second time as an instructor. He spent some time near Wash DC, and his last duty station was Rota, Spain, which was really cool.

The second time that we were in Japan, he was on a few of these, including this one