Megan and Murray McMillan

spectrogram of decoded sounds from a Russian selcall system [source]

One fascinating find in our research into this project was the existence of “Numbers Stations:” radio stations of unknown origin which broadcast strings of spoken numbers over shortwave radio in various languages. We had unknowingly crossed paths with this idea before, in Wilco’s album Yankee Hotel Foxtrot, which takes its title and many of the samples from a particular numbers broadcast.

Numbers stations are quite mysterious and have a dedicated following of shortwave radio enthusiasts and decoders. The running theory is that these stations are transmitting nearly unbreakable coded messages, but no one really knows, because no official agency will acknowledge their existence. Here’s a story NPR did on the phenomena in 2004.