A backup plan makes good military sense, and the properties of radio waves between 3 MHz and 30 MHz, especially the ability to bounce off the ionosphere, make HF radio a perfect fit. The United ...
It appears the relaxed rules would apply only to some bands, notably some VHF and UHF ... That’s around 475 kHz and 136 kHz. Ham radio operators have long used digital modes like radio teletype ...
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