Hunting them out on shortwave radio and listening to them at all hours after midnight was my childhood hobby. I must have been pretty thorough, because I rarel

Hunting them out on shortwave radio and listening to them at all hours after midnight was my childhood hobby. I must have been pretty thorough, because I rarely see documentation on stations I didn't find back in the 70's and early 80's. I used to occasionally stumble on the BBC World Service Greenwich Time Signal at the right moment while searching out the number stations, and kept a list of my findings - but that is long gone now.