Incoming links: Submarine
Notably used for communication with submarines, so in particular crucial as part of sending an attack signal to that branch of the nuclear triad.
Basically, the antenna has to be very, very large, more comparable to wavelength. E.g. even for the higher pitches, we fall in very low frequency, so have a look at the size of some of the submarine VLF antennas! They are like football pitch sized.