I want to know how such a tiny device can operate at such a long
wavelength. Unfortunately, that info is classified by the FBI/CIA, and
then won't let me or any USA citizen find out about it.


No X-files stuff needed.....

The secret is that the receiver only needs a tiny amount of bandwidth,
not more than a few hertz.
So even with a teensy, tiny, itsy-bitsy, microscopic signal, all that
an antenna that's much shorter than a wavelength can capture, that's
still enough signal to be discernible.

A cheap and simple 60KHz crystal filter has under one Hertz
bandwidth. 60KHz mini crystals are like 32 cents each at digi-key.

Voila!