The Last Elephant Cage is nsa's wonderful documentary about the massive and monotonous FLR-9 antenna system, and the 15-minute NSA documentary introduces the FLR-9 "Elephant Cage" antenna in Anchorage, Alaska.
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Netizen reviews:
Alexander (dl4no):
It's a big device, but completely useless to the average radio enthusiast: they need this type of device so as not to miss the direction of a very sporadic gearbox. In addition to what is shown in the video, another use of this system is to look for the location of foreign submarines.
If the other side does not know where the submarine is, then the submarine will become more valuable. However, even submarines must communicate with their command from time to time. When they have to transmit over shortwave, they will certainly try to reduce the transmission time.
Nazi u-boot groups coordinated attacks on Allied convoys through a single Morse code letter. In the long run, this did not help them, as the allies developed a directional system with two ring antennas at an angle of 90° and displayed on an oscilloscope.
As a general radio enthusiast, you can use a rotatable antenna (such as Yagi) or a receiving antenna. Your primary concern is suppressing any signals from other directions so that you can figure out what interests you.
I'm sure that today's U.S. satellite systems work the same way as the global kiwi sdr system: knowing the exact location of the receiving station and having a very accurate time base, you can measure the relative transmission delay and derive the transmitter's position information from it.
The last elephant cage did not happen by accident in Alaska: the short-wave propagation near the magnetic pole was very unstable. Perhaps most of the satellites that do this work today did not fly as far north or south: for quite some time, they will fly over areas of little interest.
Paul Evans:
Submarines use vlf around 5 khz to 50 khz. Because they have high frequencies on them, it's been a long time.
Zach Schindler:
Funny story. I worked in San Diego in 1980 and went to Imperial Beach to see the FLR-9 there. Oddly enough, you can stroll along the beach and get very close to it. Back at the hotel, I rummaged through the phone book and found the number of the Navy Radio Receiving Facility (NRRF) that listened to the radio. I made a phone call and started asking questions about arrays. Before I dared to say more, the guy on the other end of the phone asked me how I got that phone number. I said it was in the phone book and then hung up quickly.
Walter-ac4im:
I work in Italy and have one at San Vito Air Terminal.
cinnabar:
I was born in Brindisi (about 10 km from the base) and I remember seeing the antenna array of san vito dei normanni on the roof of my apartment. You can see the elephant cage from a distance. Really big.
Don Marshall:
Will there be another radio/radar system that uses a similar antenna? There are two distinctly hollow circles to the west of the two former sac bases (kinross, ki sawyer) in northern Michigan, west and east of the escape point (sawyer). These locations are not listed as flr sites. Will there be another radio/radar system that uses a field antenna system? I'm curious that these areas are still clearly visible long after retirement. Thanks for your insights!
I think these are for parachute practice.
Jake Brodsky, ab3a:
My hay fields are not big enough. I also need 30 acres...
Here comes the uncle:
Have you ever seen an antenna system like this?