In the early 1970s, amateur radio enthusiasts began picking up strange transmissions on the outer reaches of the spectrum. These shortwave signals, buried between shipping forecasts and commercial stations, would broadcast bizarre music and creepy mechanical voices reading out long lists of numbers. And as the Cold War intensified, more of these so-called numbers stations began flooding the fringes of the airwaves. They’re illegal to transmit, mathematically impossible to decode, and no government has ever officially acknowledged their existence. But there are some compelling theories about their origin and purpose.
Most stations begin their broadcasts with music of some kind. One nicknamed The Swedish Rhapsody plays a distorted music box version of Hugo Alfvén’s famous composition of the same name. The Lincolnshire Poacher, one of the most well known numbers stations, plays a synthesised version of the traditional English folk song. This is an announcement to the receiver that the numbers are about to begin, which are usually read out in groups of five by a staccato, machine-generated voice, sometimes for as long as 45 minutes. Then the station falls silent until the next transmission. Some stations transmit the numbers as Morse code, and there have even been rare cases of them being read out live.
It’s the strange manner in which the numbers are delivered that makes these stations such an alluring mystery. Each one has its own uncanny, idiosyncratic quirks, inspiring a subculture of shortwave fanatics obsessed with recording, archiving, and unravelling their secrets. Oddities include the Tyrolean Music station, which plays recordings of Germanic folk songs and the opening notes of socialist anthem The Internationale. The Gong bookends its numbers with loud, mangled clock chimes. And the metallic voice on The Swedish Rhapsody, which begins each transmission by barking “Achtung!”, sounds eerily like a little girl.
On a station known as Ready Ready, the announcer puts on a forced English accent, perhaps in an attempt to hide its origin. And the nonsensical, comical German spoken on the Tyrolean station ("Helmut greets Franz! The sun is shining wonderfully! Our hen is about to lay an egg!") has an unusual, possibly French accent. There have been cases of numbers stations interfering with air traffic control and interrupting programmes on the BBC World Service. A live operator was once recorded reading numbers on top of the machine voice. And the Russian Woodpecker—which transmitted a repetitive tapping noise for over a decade—was reportedly broadcast from an array inside the Chernobyl exclusion zone.
Many believe the stations are a means of communicating with spies behind enemy lines, and the case of Erwin van Haarlem backs this up. He was an art dealer who moved to London in 1975 using a Dutch passport. Described by neighbours as a "pleasant oddball", he habitually changed his locks, never had visitors, and rarely spoke to anyone. He visited Russia twice during his stay in the UK and seemed to take an active interest in Soviet émigré groups, which attracted the attention of the Metropolitan Police’s Special Branch.
A surveillance operation was mounted. Detectives monitored van Haarlem's movements from a neighbouring house and bugged his phone. During the course of the investigation, £54,000 of unexplained income was discovered across multiple bank accounts. Paperwork was cleverly forged to make it seem like the money was coming from his art business, but an accountant saw through the ruse. In 1988, van Haarlem's flat was raided and detectives caught him receiving coded messages using a shortwave radio. He panicked and tried to grab a kitchen knife when the police officers burst in, but he was quickly overpowered.
Over a period of thirteen years he had intercepted over two hundred coded transmissions, all of which were five figure groups of numbers read out in Czech. He had been decoding them using a one-time pad, which detectives found hidden in a hollowed-out bar of soap. This form of encryption is famously unbreakable, meaning that van Haarlem—whose real name was later discovered to be Vaclav Jelinek—was the only person who could have possibly decoded the numbers he was receiving through the innocent-looking radio in his kitchen.
He was a Soviet spy, sent to Britain by Statni Bezpecnost, the Czechoslovak secret police. While working for the Czech government he was known for being a patriotic risk-taker, making him perfect spy material. He was given the name of a missing Dutch boy, Erwin van Haarlem, and sent on an undercover mission to the UK. At night he exchanged messages with his home country via radio, and one of his first tasks was planting listening devices in the Queen’s furniture—until his bosses realised doing so was next to impossible.
But Jelinek’s unusual behaviour blew his cover and was ultimately his downfall. He was sentenced to ten years in prison for espionage after a widely publicised five-day trial. “I have not the least doubt that you are a dedicated, disciplined, and resourceful spy,” said Judge Simon Brown at the end of the trial. “And I have no doubt that had you not been caught, you would have done whatever your controllers required you to do, however harmful that might have been to our national interest.” He, of course, denied all charges.
This case is the only direct evidence of a numbers station being used for espionage during the Cold War, and it explains why this method of communication was, and still is, favoured by intelligence agencies. Jelinek was able to intercept the messages using a simple, store-bought shortwave radio, anyone listening in wouldn't be able to decipher the code without the appropriate one-time pad, and it could never be traced back to the sender. While in Britain he infiltrated Soviet Jewish and other East European émigré groups, sending information back to Prague in magazines inscribed with invisible ink. He was even said to have dined in Parliament on one occasion, at an event attended by senior defence officials.
After the fall of the Berlin Wall, the stations dropped in number but continued to operate—and some still do. Cherry Ripe, which is believed to have been of British origin, was live until December 2009. And voice messages were heard on The Buzzer, a station that has operated since at least 1982, in September 2012. Some investigators believe modern stations may be used by drug runners in Latin America or insurgents in war-torn countries. No organisation has ever admitted to a specific broadcast, although in an interview with the Daily Telegraph a spokesman for the Department of Trade and Industry said, with unusual opaqueness, that the numbers stations “are not for, shall we say, public consumption.”
An archive of numbers station recordings was released on CD in 1997. The Conet Project spans four discs and contains 157 tracks, some of which have been sampled by musicians including Wilco, Jóhann Jóhannsson, and Boards of Canada. Numbers stations have also featured in the TV series Lost and, more recently, horror anthology Stories Untold. There's something fascinating and strangely unsettling about the recordings, and it’s no surprise they’ve captured the imagination of so many writers and artists over the years.
The surreal, inscrutable nature of numbers stations almost urges you to listen in, which seems odd for something intended to be secretive. But perhaps the difficulty of decoding the messages is what makes their operators broadcast them so brazenly. And whoever is transmitting them is doing so at great expense, not to mention breaking countless international broadcasting laws. But while Erwin van Haarlem's plot was exposed, hundreds of other stations remain a complete mystery, and unless anyone involved comes forward, probably will forever.