from Hacker News

The world's largest "radio" station (2005) [pdf]

by ritabratamaiti on 6/20/23, 9:20 AM with 20 comments

• by posnet on 6/21/23, 6:32 AM

  Also of interest are the Nightwatch planes for use as mobile command posts in the event of a nuclear strike. They are able to trail a 5 mile long cable to act as a massive transmitter to also contact submerged ballistic missile submarines.

  https://en.wikipedia.org/wiki/Boeing_E-4#Lower_lobe

• by ianpenney on 6/21/23, 4:35 AM

  There are some Amateurs who’ve used the 2200m and 630m wavelength bands. Mostly using Morse Code, FT8 and WSPR modes as they are narrow bandwidth weak signal modes.

  https://youtu.be/FuugH6jn9rc

  https://www.qrz.com/db/?callsign=dl4eai

  In fact some of them appear to be transmitting FT8 even today.

  https://pskreporter.info/pskmap.html?preset&callsign=ZZZZZ&w...

• by jakedata on 6/21/23, 1:22 AM

  While I was passingly familiar with the system previously, this came as a bit of a surprise: "...faculty and researchers at the Michigan Technological University (MTU) School of Forestry and Wood Products have found that the Project ELF’s antenna grid makes the trees grow faster."

• by weinzierl on 6/21/23, 8:57 AM

  This is an interesting, but older document dealing with stations going down to a couple of Hertz. The lower the frequency, the larger the antenna and therefore the station needs to be.

  Currently probably the HAARP station[1] in Alaska would qualify as the largest radio station. It goes down into the 0.1 Hz range. From my limited understanding it is only possible to do so, because it basically utilizes the athmosphere itself as antenna.

  [1] https://en.m.wikipedia.org/wiki/High-frequency_Active_Aurora...

• by hatsunearu on 6/21/23, 6:58 AM

  You can actually receive those 3-30kHz signals (which are still being broadcast around the globe today) with a garden variety soundcard, as long as you have a suitable antenna (which actually isn't that hard to build, since you don't need a particularly efficient antenna to receive signals). Helps that you can get sound cards with ridiculously high SNRs (compared to say, regular radio receivers) for dirt cheap.

• by progre on 6/21/23, 4:05 AM

  See also: https://grimeton.org/en/

  An old military guy told me that Grimeton station was unofficially used to send messages to submerged subs well into the 1980:ies

• by ReactiveJelly on 6/20/23, 10:50 PM

  See also the Wikipedia article on the concept: https://en.wikipedia.org/wiki/Extremely_low_frequency

• by dang on 6/21/23, 4:44 AM

  Anybody have a year for this?