A site dedicated to format changes? Why not; what’s more historic than when something begins or ends? The Format Change Archive is your home for airchecks of the beginnings and endings of some of the most historic radio stations (and some you may never have heard).

"Numbers stations are shortwave radio stations of uncertain origin. They generally broadcast people reading streams of numbers, words, or letters (sometimes using a phonetic alphabet)." Here's where that "yankee hotel foxtrot" sample came from.