They do: https://en.wikipedia.org/wiki/Frequency-hopping_spread_spectrum https://en.wikipedia.org/wiki/Frequency-hopping_spread_spect... https://en.wikipedia.

They do: https://en.wikipedia.org/wiki/Frequency-hopping_spread_spectrum https://en.wikipedia.org/wiki/Frequency-hopping_spread_spect... https://en.wikipedia.org/wiki/Hedy_Lamarr https://en.wikipedia.org/wiki/Hedy_Lamarr The really clever counterpart is how to transmit through your own spread-spectrum jamming. Quiet slots in the jamming must be manipulated in the same way as the active broadcast. For example, this allows communication to a ground convoy that is jamming all frequencies to prevent wireless remote-control IED detonation.