I'd often find strange broadcasts when sitting in the shelter after marching all day where I was pretty much too tired to do anything but tune around until I fell asleep. I even picked up some of the mysterious numbers stations - many recording of these are found here, the Conet Project. There is even an action movie made about this subject: The Numbers Station.
It seems that international political intrigue and radio are still ongoing and, if there is ever again some sort of large scale conflict, these sorts of communication strategies will make a resurgance.
“MDZhB” has been broadcasting since 1982. No one knows why.“MDZhB”... Twenty-four hours a day, seven days a week, for the last three-and-a-half decades, it’s been broadcasting a dull, monotonous tone. Every few seconds it’s joined by a second sound, like some ghostly ship sounding its foghorn.