While Numbers Stations are somewhat well-known and have been featured in many TV shows (most notably, Lost), and even a movie, the similar subject of Card Stations has seemingly been lost to time.
Card stations were discovered in the 60s and 70s in rural America. Similar to numbers stations, they were shortwave radio stations that broadcast robotic voices putting out a string of information. But instead of numbers they would be playing cards. Sometimes it would be a long list of playing card values, often with designation “face up” or “face down.” And other times it would broadcast specific instructions like, “Deal the nine of clubs. Discard the eight of diamonds.”
Unlike numbers stations, which seem mysterious but whose purpose is fairly well understood, card stations have never been fully explained. They existed only briefly and there was never a determination whether they too were designed to code information to intelligence officers or if they served some other purpose. Some suggest they were a hoax and served no purpose at all.
Very little documentation remains on card stations. Most of my information on them comes from off-line research, proving them to be a true mystery indeed!
Here’s one of the few things I was referred to online during my research. It’s a piece of audio that purports to be from one of the original card stations.
Here is the same video run simultaneously with audio of black noise, a signal that was first discovered in the card stations audio. Early studies suggested black noise had the effect of both disguising and amplifying the messages in the card station recordings. I’ve been unable to uncover further studies on this topic.