“The Last Elephant Cage” is a fascinating NSA documentary about the monolithic FLR-9 antenna system

Many thanks to SWLing Post contributor, Andrea Borgnino (IW0HK), who shares the following video–a 15 minute NSA documentary–about the FLR-9 “Elephant Cage” antenna in Anchorage, Alaska.

Click here to view on YouTube.

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21 thoughts on ““The Last Elephant Cage” is a fascinating NSA documentary about the monolithic FLR-9 antenna system

  1. Alexander, DL4NO

    That is a big installation, but completely useless for civilians: They needed this type of equipment to not miss the direction to very sporadic transmissions. Another usage of such systems than shown in the video was the position finding of foreign submarines.

    A submarine gets much more valuable if the other side has no idea where it is. But even submarines have to communicate with their command from time to time. When they had to do it by shortwave, they definitely tried to reduce the duration of their transmissions as far as possible.

    The U-Boot swarms of the Nazis coordinated their attacks on allied convoys by single Morse code letters. On the long run it did not help them as the allies developed a direction finding system with two loop antennas at a 90° angle and a display on an oscilloscope.

    As a civilian you use turnable antennas like yagis or receiving antennas like Beverages. Your primary concern is to suppress any signals from other directions so you can dig out what interests you.

    I am sure the US today have satellite systems working like the the worldwide Kiwi SDR system: With knowing the exact location of the receiving station and having a very exact time base, you measure the relative transmission delays and derive the position of the transmitter from this information.

    The last elephant cage is in Alaska not by chance: The shortwave propagation near the magnetic poles is very erratic. Perhaps most satellites that do this job today do not fly so far to the north or south: For quite some time they would fly over areas that are of hardly any interest.

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  2. Zack Schindler

    Funny story. I was in San Diego on a job in 1980 and went down to Imperial Beach to take a look at the FLR-9 there. Weirdly you could get pretty close to it by walking along the beach. Once I got back to my hotel I looked in the phonebook and found the number for the Naval Radio Receiving Facility (NRRF) which was the listening post. I called the number and started to ask a question about the array. Before I could say much the guy on the other side of the line asked me how did I get that phone number. I said that it was in the phonebook and then quickly hung up.

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    1. Dan

      I was born in Brindisi (about 10 km from that base) and I remember I used to go on top of my block of flat to look at the antenna array in San Vito dei Normanni. You could see the elephant cage from far away. It was really big.

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  3. Don Marshall

    Would there be another radio/RADAR system that used a similar antenna? There are two pronounced open circles at two former SAC bases in northern Michigan (Kinross, KI Sawyer) West of the runaway (Sawyer) and east (Kinross). These locations are not listed as FLR sites. Would there be another radio/RADAR system that used an open field antenna system? I’m curious how theses areas remain clear long after decommissioning. Thanks for any insight!

    Reply
    1. Chuck Rippel

      I had one very close to my back yard, about 8 miles actually. There was one located Naval Security Group, Northwest in Chesapeake, VA. The state line runs through the property on which it was located.

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