Spy Radio: Numbers Stations

Today we're going to point our skeptical eye at something that's been intriguing amateur radio enthusiasts since the cold war: so-called numbers stations, mysterious shortwave radio broadcasts sending coded messages to the world at regular intervals. Some say they are government intelligence agencies sending instructions to deep-cover operatives in foreign countries. Some say they are integral parts of nuclear arsenals. Some even say that if you're caught listening to the wrong one at the wrong time, you might mysteriously disappear one night.

Shortwave radio occupies the frequency range between 3 and 30 MHz, and most numbers stations can be found in the range between 2 and 25 MHz. The benefit of shortwave is that your transmission can potentially cover the entire world, given the right conditions. It's one way, but if all you need to do is send someone else a message that you want to be sure they're able to receive, shortwave is a great way to do it. Some histories state that numbers stations have been around in one form or another since World War I, but it was toward the end of the cold war in the 1980's when they really started gaining popularity. Many early numbers stations used Morse code or an actual person's speaking voice, but today most numbers stations use automated voices like you hear when you call information on the telephone. Today many of the numbers stations are switching to single side band. The typical numbers station begins its broadcast with some recognizable tone or statement, and then proceeds to read off 5-character code groups. It is widely suspected that these are encrypted messages that can be decoded by a listener using a one-time pad. A one-time pad is a character replacement key that's used only once. Since it's never reused, one-time pads are extremely difficult (in fact, virtually impossible) to crack. You can Google for "numbers stations" and you'll find plenty of websites that list them by frequency and by schedule, so if you get ahold of a shortwave receiver you can actually sit down and listen to them. They are real, and they are broadcasting, right now.

Now, whenever I hear claims about spy networks or secret coded radio broadcasts, my skeptical radar goes into Red Alert mode, like Moneypenny's pulse when 007 enters the room. If you tell me there's a mysterious coded radio broadcast on shortwave at the same time every day, my first reaction is not likely to be to grab my tinfoil hat and shout "The government's spying on me!" When I first heard about numbers stations, I asked a few friends, and I got some pretty reasonable answers. For one thing, all over the world are floating oceanographic buoys, and all throughout every day they transmit their tide, temperature, and weather data via radio. I did a bit of searching online and found a lot of information about a number of different networks of these buoys, but none broadcast in the shortwave band, rather they are quite a bit higher, above 900 MHz. They also use radio modems for data transmission, there would be no need for them to include spoken text. But even with these differences, it seems likely that at least some of the "mysterious radio stations" that amateurs have found are probably nothing more interesting than oceanographic buoys, or other remote automated stations transmitting who knows what kind of mundane information.

But most of the numbers stations you can read about online are clearly nothing of the kind. One of the most well-known numbers stations is called the Lincolnshire Poacher, named after the song that the broadcast always starts with. Enthusiasts using direction finders have tracked it down to an array of curtain antennas inside the United Kingdom's Royal Air Force Base at Akrotiri on the island of Cyprus. Note that Cyprus is right off the coast of Syria and the Middle East. After the introductory music, the Lincolnshire poacher repeats some coded 5-digit series, which nobody has ever managed to decode, presumably excluding the intended recipients: [play sample]

The prevailing theory, that many of these numbers stations are in fact used by intelligence agencies to transmit information to spies located in foreign countries, has been proven true in at least a few cases. In 2001, nine days after 9/11, the US Defense Intelligence Agency arrested one of its own, senior Cuba analyst Ana Montes. Among a wealth of other evidence against her, she had been using a commercially available shortwave radio receiver to receive coded messages from a numbers station known to be originating in Cuba. This was only strike two of a series of interceptions of intelligence broadcasts from Cuba. One of the best known numbers stations, called ¡Atención!, came into the limelight at the 1998 conviction of the so-called Wasp Network of spies from Cuba. The FBI had entered their apartment and copied a cryptography program off of their laptop computer. It was found that every day, they would listen to the ¡Atención! station, enter the numbers into their laptop, and use the program to decode each day's instructions using a one-time pad. Here's a sample of ¡Atención!: [play sample]

Some numbers stations have purposes that are more obscure, even though they may still have a government connection. One of them is called Yosemite Sam. Yosemite Sam began broadcasting in 2004 and has been tracked down and found to be located near Albuquerque, NM, which is near a whole host of military facilities including the Los Alamos National Laboratory and White Sands Missile Range. Sam transmits an 800 millisecond data burst followed by a line from a 1949 Bugs Bunny cartoon, on a number of different frequencies. Every 40 seconds, the broadcast moves to the next frequency and repeats. Here's a sample transmission: [play sample]

Of course the Russians are in on the game too, demonstrated by this station known simply as "the Buzzer" which broadcasts around the clock from a Moscow suburb: [play sample]

Why transmit a meaningless buzz all the time? There are a few theories. One is simply that in order to keep a frequency, you have to actually use it, or it will be reallocated to someone else. The Russians may want to keep this frequency open and available should they need it in a time of national emergency. The same might apply to Yosemite Sam or to any of a number of other numbers stations. In fact, this explanation need not even be military. Private companies may also have similar needs. Amateur radio enthusiasts might also have some reason to do this. Russia has about 150 radioisotope thermoelectric powered lighthouses along their arctic coast and it's been postulated that the Buzzer might somehow be used in monitoring them.

There are other perfectly rational explanations for at least some numbers stations that don't involve Tom Clancy scenarios. It's been suggested more than once that some of the numbers stations, particularly those coming from Central and South America, could be drug traffickers giving delivery instructions.

What about the stories that you can be arrested if you're caught listening to numbers stations? Assuming you're not a spy who actually is decoding these messages in a treasonous kind of way, you're not doing anything wrong, you're just receiving electromagnetic radiation that someone is transmitting into your home. Lucille Ball's dental fillings did that. In some countries, notably the UK, this is actually illegal. But, it has nothing to do with numbers stations. In the UK it's simply illegal to receive any radio transmission that you're not licensed for. Obviously it's the type of crime that ordinary listeners not involved in some misuse of the airwaves are unlikely to actually get arrested for.

The thing I like about numbers stations is that it's one case where the spooky explanation, the one that would appeal most to the conspiracy theorists, actually turns out to be the right one in at least some instances. We do know that some numbers stations do exist for the purpose of international espionage, and that's pretty cool. Do all numbers stations exist for that purpose? Certainly not. There are a number of plausible non-espionage scenarios that, if true, would result in broadcasts consistent with some of the numbers stations out there. They're a fun mystery, made even more fun by the high stakes of the spy game.

By Brian Dunning
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