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voucher420 t1_iu6376h wrote

Reply to comment by KMjolnir in TIL that in 1968 the US Navy proposed turning 2/5ths of Wisconsin into a giant underground radio antenna so orders could still be sent to submarines following a nuclear attack on America by DeadForDecember

Like 2/5 of Wisconsin huge?

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no_step t1_iu69lmt wrote

It was an ELF, extremely low frequency transmitter. Those radio waves need extremely large antennas and a particular type of soil

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[deleted] t1_iu63o89 wrote

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TacTurtle t1_iu6bn25 wrote

It is actually more that the wavelength for extremely low frequency radio requires extremely long antennas for efficient transmission and reception - not an electrical hardware size issue.

Wavelength = speed of light / frequency so as frequency goes down, wavelength (and antenna size) go up.

Subs use a long antenna cable they can extend and tow behind underwater for ULF radio transmission and reception.

Faster transmission with a shorter antenna requires getting closer to the surface for higher freq radio which will not penetrate water as easily.

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[deleted] t1_iu6c0lc wrote

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TacTurtle t1_iu6fhd4 wrote

The actual generation and radio equipment could fit in a couple shipping containers or a small building, it is the antenna that is big.

3MW is small enough power you can get them as pre-packaged skid-mounted units like https://www.westernstatescat.com/power-systems/electric-power/gas-generator-sets/cg260-12-2100kw-3000kw3mw-gas-generator-2/

Example: check out this weather radar array - radar is radio broadcast and receive, just at much higher frequency. WSR-88D weather radars for reference are almost 1MW. The Wisconsin ELF was 2.6Mw.

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