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Numbers in the Air

Numbers stations are mysterious shortwave radio stations, broadcasting streams of numbers or letters using the phonetic alphabet, by voice, Morse or digital tones. The messages are usually groups of four or five numbers or letters and are typically repeated by reading each group twice or repeating the entire message. These stations are unlicensed high power HF transmitters, broadcasting worldwide in various formats and languages.

They do this day and night on a wide range of frequencies and it's been going on for decades, yet no single private, commercial or government agency ever stepped forward to officially confirm that they are responsible for these strange broadcasts. However, today there is enough evidence that these stations are used by Intelligence agencies to send encrypted messages and operational instructions to their agents in covert operations abroad.

The messages are broadcast on very powerful shortwave transmitters with frequencies ranging from 3,000 to 30,000 Khz. The numbers or letters are spoken in many different languages, usually a female voice, but sometimes male or those of children. Many of the broadcasts are mysterious mechanically or electronically generated voices. The stations often use introduction signals as a beacon, prior to a actual message. These repeating phrases, electronic sounds or music enable the receiver to adjust his radio to the desired frequency. In recent years, many numbers stations switched from voice or Morse to digital tones.

Radio amateurs monitor these broadcasts and they sometimes give nicknames to a station, according to its typical introduction phrase (e.g. the Cuban "Atencion" station), prelude music (Swedish rhapsody) or language of the voice (Bulgarian Betty). Some stations are called counting stations, because of their introduction signal. An example is the Cuban "Atencion 1234567890".

The Cold War era, from the 1950s until the end of the 1980s, is known for its numerous and very active numbers stations, not by coincidence the heydays of espionage. Many of the broadcasts came from the Eastern-block countries, China and Cuba, but also from several Western countries.

After the 1989 fall of the Berlin Wall, the number of stations significantly decreased from countries like East and West-Germany, Yugoslavia, Hungary or Bulgaria. The voices of those stations were mostly Russian or German. However, several decades after the end of the Cold War, stations remain active in the former Soviet-Union, Europe, and in North and South America, and new stations continue to appear all over the world.

Most numbers stations use a basic format to send the streams of numbers or letters. Some stations broadcast every day at a fixed hour, and disappear after a few days or weeks. Other stations have an irregular time schedules and appear and disappear over time. One of the most regular numbers stations ever was the Lincolnshire Poacher (E3 Voice), named after the English folk song that was used as its interval signal. After transmitting the very recognizable melody and a call-sign for about ten minutes, the message was sent by an electronic English-accented female voice in groups of five figures. The station aired every day from the 1970s until 2008. A simple small shortwave radio was sufficient to capture the Lincolnshire Poacher. It is believed that the station broadcast from the RAF Akrotiri basis in Cyprus and that is was operated by the British Secret Intelligence Service. Unfortunately, the world of radio waves lost a true Cold War icon when the station went off-air in 2008. Its Asian sister station Cherry Ripe however is still active.

Why Numbers Stations

Although no government or legal broadcaster ever acknowledged any involvement in these broadcasts, it is obvious that the costs and organization of such large-scale illegal broadcasts can only be supported and approved by government agencies. Countries like Russia, China and the United States exploit large shortwave antenna parks in their own country and at their embassies abroad.

The content and structure of the messages are identical to cryptographically encrypted messages. The groups appear to be totally random and without any logical order or meaning. It is assumed, and confirmed in several uncovered spy cases, that the seemingly random numbers or letters are actually one-time-pad encrypted messages. Numbers messages were used extensively in the Second World War. The British Special Operations Executive (SOE), the American Office of Strategic Services (OSS) and many other intelligence agencies used them to communicate with their espionage and sabotage teams, operating behind enemy lines.

History has proven this to be a most secure method. One-time pads are sheets or booklets with keys that consist of series of truly random numbers or letters. Enciphering and deciphering a message only requires pencil and paper and some basic calculations. Each message is enciphered with a unique one-time pad which is destroyed after one-time use. If properly applied, one-time pad is the only system that is proven to be mathematically unbreakable. For more information, visit my one-time pad page.

The one-way shortwave broadcast has many advantages for Intelligence agencies. Powerful shortwave transmitters reflect their signal many times between the earth's surface and the ionosphere, carrying them over very long distances. This enables Intelligence agencies to send messages to agents located in far away countries. The many reflections also make it difficult to accurately locate the transmitter and find out who is broadcasting. The enormous, almost global range of shortwave makes it impossible to identify the country of destination, let alone the person who receives the message.

Therefore, there is little risk of exposing the secret agent who receives a message. A simple commercial shortwave world-receiver can pick up a messages and the agent doesn't need a compromising special receiver or crypto equipment. He can easily carry and hide a large number of one-time pads in small booklets or on microfilm, and the manual one-time pad system, although slow and elaborate, requires nothing more than a pencil and paper. Therefore, numbers stations are an ideal method of covert one-way communication to illegal agents abroad.

Evidence for use as Spy Stations

Over time, declassified documents from court trials and Intelligence agencies revealed the truth about these mysterious numbers stations. They also show that the era of spy stations and espionage is far from over. This information enables us to discard all stories about numbers stations being so-called weather buoys, shipping reports or other decoy fairytales. Several spies have been caught in possession of shortwave radios and one time pads. Given the widespread and frequent use of numbers stations, the published cases are undoubtedly only the tip of the iceberg.

In 1962, Soviet GRU Colonel Oleg Penkovsky was arrested by the KGB and charged with espionage. During a search of his Moscow apartment, KGB found one-time pads, instructions on how to receive and decipher encrypted radio messages, a Sony shortwave radio, a Minox camera and other spy equipment, cleverly hidden inside a secret compartment in his desk. More info, Andrei Sinelnikov [Rus] [Eng].

Documents of the East German Ministerium fur Staatssicherheit (Stasi), describe in detail intercepted packets, destined for German CIA agents that lived in the former DDR, containing one-time pads, instructions on how to receive numbers messages on shortwave radio and the deciphering procedures for these messages. These are published on the SAS und Chiffrierdienst website.

Michael Michnowski defected together with Stasi agent Werner Stiller from East Germany in 1979. He published his story about the preparations and the defection. In that story he describes the covert communications with the Bundesnachrichtendienst (BND), West-German intelligence, and how they used a shortwave radio to receive one-time pad encrypted instructions, sent by BND numbers stations. You can watch a video of a speech and Morse generator used by the East-German Stasi, or listen to the voice output (mp3). This is the machine behind the infamous East-German lady. The machine was stangely enough labeled in English, but this was because it was exported to many other Eastern-block countries.

In 1988 Vaclav Jelinek, a Czech StB spy who operated under the false identity of Erwin van Haarlem, was arrested by British Special Branch detectives while receiving a numbers message on a shortwave radio in his London apartment. One-time pads were found on microfilm, hidden in bars of soap. The pads enabled the detectives to decipher some of the received messages, which were later used in court. Jelinek was sentenced to ten years of imprisonment.

More recently, there were several spy cases in the United States, related to Cuban numbers stations. In the 1998, the so-called Cuban Five from the Wasp Network spy ring, agents of the Cuban DGI (Dirección General de Inteligencia), received instructions by encrypted messages that were sent each day by the Cuban HF numbers station "Atencion".

Another one was the Ana Belen Montes case, a senior US Defense Intelligence Agency analyst, spying for Cuba. She was arrested in 2001 and the federal prosecutors stated: "Montes communicated with the Cuban Intelligence Service through encrypted messages and received her instructions through encrypted shortwave transmissions from Cuba". More on the Belen Montes case in this FBI affidavit (pdf).

In 2006, Florida International University professor Carlos Alvarez and his wife Elsa Alvarez were charged with espionage and acting as agents for Cuba. The US District Court Florida stated: "Defendants would receive assignments via shortwave radio transmissions. These messages were encoded in five-digit groupings. Once received, Defendants would input these coded messages into their home computer, which was equipped with decryption technology contained on a diskette" More in the Alvarez sentencing.

US State Department official Walter Kendall Myers and his wife Gwendolyn Steingraber Myers were arrested in 2009 on charges of serving as illegal agents of the Cuban government for nearly 30 years. They acknowledged having received encrypted messages from the Cuban Intelligence via a shortwave radio they possessed. The Columbia State District Court indictment stated that "Cuban intelligence broadcasts encrypted shortwave radio messages in Morse Code or by a voice reading numbers" and also that "It was part of the conspiracy that Cuban Intelligence would and did broadcast shortwave messages in Morse code which were receive by Kendall Myers". More about this case in the Myers court indictment. More information about Cuban numbers stations and agent communications procedures in the Cuban Agent Communications (pdf) Paper.

Note: all espionage radio equipment images on this page are copyrighted by Detlev Vreisleben. More about him on License To Shoot.



Speech and Morese Generator © Detlev Vreisleben

East-German Speech & Morse Generator "Stimme"
© Detlev Vreisleben
(watch machine in action)


Shortwave agent receiver  © Detlev Vreisleben

Specially designed interference-radiation free shortwave agent receiver type 32310.
© Detlev Vreisleben


SW-MW Convertor © Detlev Vreisleben

A 1950s SW to MW converter to receive messages from BND (West-German Intelligence) on a normal MW radio. In those days, commercial SW radios were not available in East-Germany. Unfortunately, the converter was notorious for its unwanted and strong interference radiation. © Detlev Vreisleben


A standard commercial shortwave receiver, ideal to covertly receive numbers messages. If discovered, this radio will not arouse any suspicion.


© Canadian Security Intelligence Service

A seemingly innocent AA type battery, cleverly crafted to contain clandestine items such as one-time pads or microfilm. This item was used by a foreign intelligence service.
© Canadian Security Intelligence Service


CIA one-time pad, used by Alexander Ogorodnikov.
Source: KGB Archives

(click the images to enlarge)

From Cold War to Cold Peace

Are numbers stations still useful in this age of global communications, Internet and satellite links? Yes! The so-called end of the Cold War did not bring a significant decrease in espionage activities. In the contrary, the Cold War is merely replaced by a Cold Peace where espionage is booming. In today's world, with the globalization of economics, politics and conflicts without borders, covert and illegal agents of Eastern, Western, Asian and Far East countries still operate extensively in each others countries to gather Intelligence and run operations. They still need a secure way to receive their operational instructions and messages. However, today, all modern communication systems are controlled by computers and are therefore by definition insecure.

Telephone, Internet and even satellite transmissions can be monitored. E-mails can be intercepted and read. Some government agencies have the money and resources to monitor communications and trace both sender and receiver. An example is the huge ECHELON project which globally intercepts and identifies all kinds of communications. In times of conflict, countries can simply block the Internet or other communications, or even simply switch off satellites. There have been successful tests to destroy satellites with missiles, making satellite communications unreliable during a serious conflict. Or did you really believe to continue using telephone or Internet between, let's say, Russia and the United States, if they where at war with each other?

Imagine a war broke out and intelligence personnel are operating behind enemy lines. The only secure and reliable way to communicate with them would be the good old-fashion long distance shortwave radio. But even in times of peace, some covert operations are so sensitive that discovering them would bring governments big problems or embarrassment. It is believed that some numbers stations continuously send fake messages, just to keep the lines open, ready for use. Those who monitor these stations are unable to notice when a station suddenly changes from sending random numbers to operational encrypted traffic. A good example is the Lincolnshire Poacher, sending messages of 200 groups, each and every day, for almost 40 years. Reasons enough why numbers stations are still active and useful. With their long and outstanding career of more than 70 years, the numbers stations have become an icon of espionage.

And still, every single day, numbers messages are transmitted all over the world, spoken in English, Russian, Spanish, Chinese and many other languages. Who's broadcasting them and, even more intriguing, who's listening to them...?

Some recordings

Lincolnshire Poacher (863 Kb) English female voice, MI6, introduced by a melody
Swedish Rhapsody Child (188 Kb) This is a mechanical child voice, introduced by an 'ice cream man' melody
Attencion Station (250 Kb) The well known Cuban Attencion station, broadcasts for Cuban agents in the U.S.
Yankee Bravo (131 Kb) German female voice, probably of KGB origin, introduced by the call sign YB
Russian Male (83 Kb) Russian male voice, KGB
East-German 'Stimme' (365 Kb) Voice output of the East-German 'Stimme' Generator

Right-click the icon and select 'save target as' to download the mp3 file.

Numbers on the Internet

Numbers messages can also be distributed through the Internet. The Numbers Relay Page (NRP) is an online method to post numbers messages. The NRP is an easy way to exchange encrypted messages without disclosing the sender or receiver and requires only a computer with Internet browser.

More about the NRP on this page.

More on this website

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© Copyright 2004 - 2014 Dirk Rijmenants

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