Shortwave radio signals, which occupy the radio frequency band between 3 and 30 megahertz, have the unique ability to bounce or “skip” off the earth’s ionosphere, allowing them to propagate over vast distances. This has attracted a devoted international community of shortwave radio enthusiasts, who exploit the unique properties of the medium to listen to and communicate with shortwave stations from around the globe. But among the vast ecosystem of amateur broadcasters, international news services, and emergency communications networks, every so often shortwave operators stumble upon something truly eerie and bizarre. Take the frequency 4625 kilohertz, known to radio amateurs as UVB-76 or simply “The Buzzer.” First discovered in 1985, The Buzzer broadcasts nothing but a constant, monotonous buzz, made up of two distinct tones repeating 25 times per minute. Every few weeks or so, this buzzing is interrupted by a voice, which proceeds to read out a string of random words or numbers in Russian. The buzzing then resumes, carrying on 24 hours a day, 365 days a year. While the source of UVB-76 has been traced to two sites outside Moscow and St. Petersburg, no agency or organization has ever admitted to operating the station. This had lead to endless speculation as to the Buzzer’s function, with some theorizing it is used to probe the ionosphere for radio interference, others that it is part of Russia’s infamous “Dead Hand” system, designed to automatically launch the nation’s nuclear arsenal in case of attack. More likely, however, is that the Buzzer belongs to a curious breed of radio stations whose origins lie in the shadowy world of Cold War espionage and which continue to faithfully serve the world’s intelligence services to this day. Welcome to the strange and mysterious world of Numbers Stations.

Numbers Stations are nearly as old as radio itself, with the first examples appearing in Europe during the First World War. Their numbers exploded, however, in the Cold War era, with the phenomenon first coming to the attention of radio amateurs around the mid-1970s. Numbers Stations are so-named because they typically broadcast nothing but seemingly random strings of numbers, letters, or sometimes words. These messages are transmitted in a variety of formats, including Morse Code, phase or frequency shifting, and voice – either real or synthesized. Each string of numbers is usually preceded by a unique identifier or callsign, which often forms the basis for the colourful nicknames given to the stations by radio amateurs. One of the most famous numbers stations, the “Lincolnshire Poacher,” used as its callsign the first bars of the English folk song of the same name, synthesized to sound like a calliope organ and repeated 12 times. This was followed by a British-accented female voice reading a string of numbers. First heard in the 1970s, the Lincolnshire Poacher initially broadcasted from Bletchley Park in Buckinghamshire but later moved to the Royal Air Force Station at Akrotiri on the island of Cyprus. It ceased broadcasting in 2008. A similar station called Cherry Ripe, which also used an English folk song as its callsign, broadcast from somewhere in the south Pacific until 2009. Other famous Numbers Stations include “Ready! Ready!” “Allo! Allo!” “The English Man”, “The English Woman”, “Oblique”, “Swedish Rhapsody”, “Nancy Adam Susan”, “Cynthia”, “The Babbler”, “Squeaky Wheel” “The Pip”, and “Magnetic Field”, the latter named for its use of a song by French electronic composer Jean-Michel Jarre. While many of these stations broadcast in English, not all originated in English-speaking countries. For example, “Ready! Ready!” and “The Babbler” are thought to have originated in Bulgaria, “The English Man” in Russia, “The English Lady” in Ukraine, and “Oblique” in Poland.

The eerie and mysterious nature of numbers stations soon attracted a devoted community of radio amateurs, who began to actively seek out, classify, and study these enigmatic broadcasts. The number of recorded numbers stations quickly grew so large that in 1993 a station tracking group called ENIGMA 2000 developed a designation system to keep track of them all. This system classifies stations using a letter prefix indicating the type of broadcast and a number indicating its order of discovery. For example, E indicates a station broadcasting in English, G in German, S in Slavic, V in all other languages, M in Morse Code, and X in all other modes such as frequency and phase-shifting. But as obsessive and meticulous as this might sound, some aficionados have taken their obsession with numbers stations to even more absurd heights. From the moment he stumbled upon his first numbers station in 1992, British radio amateur Akin Fernandez was hooked, explaining in a 2004 interview:

“You’re listening, and all of a sudden you come across a really strong signal. It’s the most chilling thing you’ve ever heard in your life. These signals are going everywhere and they could be for anything. There’s nothing like it.”

Over the next five years, Fernandez spent nearly every waking hour meticulously recording and categorizing every numbers station he could track down. This work culminated in 1997 with the release of The Conet Project, one of the strangest albums in the history of recorded music. Named after the Czech word for “end,” which Fernandez heard often on the airwaves, The Conet Project comprised four CDs filled with over 280 minutes of excerpts from numbers stations around the world, along with a 74-page booklet detailing the background and details of each broadcast. While the album initially sold only 2000 copies, it had a strangely significant impact on the world of music, being sampled in a variety of other artistic projects including the band Porcupine Tree’s 1999 album Stupid Dream, Wilco’s 2001 album Yankee Hotel Foxtrot, and the soundtrack of the 2001 Cameron Crowe film Vanilla Sky.

But just what are these eerie broadcasts for? Are they merely pranks, placeholders for certain radio frequencies, or something more sinister? While for decades numbers stations remained one of the great unsolved mysteries of radio broadcasting, starting in the 1980s a number of international incidents finally began to shed light on their enigmatic purpose. In 1988, British Intelligence detected a strong radio signal emanating from the flat of Dutch national Erwin van Haarlem. London Police raided the flat and found van Haarlem sitting in front of a short wave radio, listening to a numbers station based in Czechoslovakia. Codebooks were later discovered in a hollowed-out bar of soap, and van Haarlem revealed to be a Czech agent named Václav Jelínek. Later that year, when the communist regime of Romanian dictator Nicolae Ceasescu collapsed, all numbers stations broadcasting from Romania abruptly stopped. And in October 2011, when German Police raided the Margburg home of Andreas and Heidrun Anschlag, they caught the couple sitting at a shortwave radio receiver, receiving coded instructions from Moscow. When interrogated, the Anschlags revealed that they always received instructions at 6PM on Tuesdays and Thursdays – a schedule that happened to coincide perfectly with a Russian numbers station known as XPA. These and other incidents have led experts to suspect that numbers stations are in fact a clever means of solving a classic problem faced by nations trying to communicate with their agents abroad.

Secure communication is one of the key pillars of spycraft. Throughout history, spies and their handlers have come up with increasingly sophisticated methods of keeping secret messages safe from prying eyes, from physically hiding them in ordinary objects – a craft known as steganography – to obscuring them using codes and ciphers. But simply rendering a message unreadable to the enemy is no guarantee of security, as merely being caught sending or receiving a coded message can be enough to expose and condemn a suspected spy. And the steady march of technology only made matters worse, for as easy as it was to intercept a letter or telegram, it was even easier to tap a phone or listen in on a radio signal. This was the dilemma facing the All-Russian Co-operative Society or ARCOS in the 1920s. Officially, ARCOS was a diplomatic body governing economic trade between the UK and the newly-formed Soviet Union. However, intercepts of encrypted Soviet radio signals by the British Secret Intelligence Service or SIS revealed that the organization was in fact a front for Soviet espionage activities in the country. In May 1927, the British Government launched a raid against ARCOS headquarters London, where they discovered a secret room filled with workers hurriedly burning reams of secret documents. Realizing that the British had been reading and decrypting their broadcasts for years, almost overnight the Soviet OGPU intelligence service – precursor to the KGB – changed the way it communicated with its agents abroad. Most significantly, the OGPU switched to an enciphering system known as one-time pads, randomly-generated single-use ciphers whose keys are the same size as the plaintext being encoded – eliminating any repeats that can be exploited by codebreakers. So long as each key is used only once, one-time pads are considered mathematically impossible to crack and an absolutely secure form of encryption. To prevent the keys from falling into enemy hands, one-time pads are often printed on water-soluble or flammable paper so they can easily be soaked, swallowed, or burned.

The absolute security afforded by one-time pads allowed the Soviets to broadcast coded messages in the open, on common civilian radio frequencies. This way, while anyone could theoretically intercept the signal, only those with the one-time key could decipher it. And as it was impossible to tell who the signal was intended for, this system provided a useful degree of plausible deniability for agents, as Akin Fernandez explains:

“This system is completely secure because the messages can’t be tracked, the recipient could be anywhere. It is easy. You just send the spies to a country and get them to buy a radio. They know where to tune and when.”

This system, known as one-way voice link or OWVL, was quickly adopted by a variety of countries, including the UK, which during the Second World War transmitted instructions to the French Resistance and other Allied agents in occupied Europe via coded messages embedded in BBC radio broadcasts. Later, SIS and other intelligence agencies established dedicated numbers stations to communicate with their agents in the field, using the long-range capabilities of shortwave radio to carry their secret messages to every corner of the globe. As espionage expert Rupert Allason explains:

“Nobody has found a more convenient and expedient way of communicating with an agent.

Their sole purpose is for intelligence agencies to communicate with their agents in denied areas – a territory where it is difficult to use a consensual form of communications.”

Indeed, while numbers stations might seem like an outmoded relic of the Cold War, made obsolete by the advent of computers, the internet, and other sophisticated communications technology, in reality quite the opposite is true. Every message sent on a computer or over the internet leaves a digital trace, making absolute security difficult to achieve without incredibly strict communications protocols and sophisticated encryption. Numbers stations broadcasts, on the other hand, are untraceable, efficient, and cost-effective, meaning this system still has a place in the modern landscape of high-tech espionage.

Perhaps the most famous recent espionage case involving a numbers station is the 1998 “Atención” case, in which five agents of the Cuban Wasp network were arrested in Miami. One piece of evidence later used to convict the agents of espionage was that they had received instructions from a Cuban-based numbers station known as “Atención”. Three years earlier, FBI agents had entered the home of a network member and copied decryption software from his laptop, allowing the FBI to decode Atención broadcasts. These messages included instructions to recruit local contacts and intelligence sources, a greeting for International Women’s Day on May 8, and a warning against accepting flights from Brothers to the Rescue, a Miami-based anti-Castro organization. Interestingly, the only reason Atención was known to be of Cuban origin in the first place is because a technical error resulted in a snippet of a Radio Havana broadcast becoming mixed in with the signal. More recently, another Cuban numbers station was involved in the case of Ana Montes, a senior Defense Intelligence Agency analyst who in 2002 was convicted of spying for the Cuban government for nearly 17 years. According to prosecutors, Montes received her instructions via shortwave radio and decoded them using one-time-pads printed on water-soluble paper. North Korea has also made extensive use of numbers stations, suddenly resuming broadcasts in July 2016 after a 16-year hiatus. This is thought to be an act of psychological warfare, meant to put Western intelligence analysts on edge.

But what of UVB-76, the mysterious “Buzzer” that barely seems to broadcast anything but its signature droning tone? While no government agency has of yet admitted to operating the station, the most likely suspect is the Russian Foreign Intelligence Service or SVR, the agency to which German spies Andreas and Heidrun Anschlag belonged. And while the Buzzer and similar Russian stations like “The Pip” and “Squeaky Wheel” do not fit the typical profile of numbers stations, experts believe this is because they are on standby, kept in reserve for a future conflict or major deployment of Russian agents. The mysterious “buzz,” then, is likely just a placeholder, meant to discourage other broadcasters from using that particular frequency. Evidence for this theory emerged in 2013 when, after nearly 30 years of nothing but buzzing and brief number strings, UVB-76 suddenly broadcast the ominous message “Command 135 Issued.” According to radio enthusiast Māris Goldmanis, this was likely a test message, meant to bring the whole broadcast system onto a simulated war footing. So as unsettling as UVB-76’s endless, monotonous drone might be, should that drone ever stop, it might be a sign that something very, very bad is about to happen.

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