Numbers station

Amongst amateur radio enthusiasts there is an interest in monitoring and classifying numbers stations, with many being given nicknames to represent their quirks or origins.

It is reported that Archduke Anton of Austria in his youth during World War I used to listen in to their transmissions, writing them down and passing them on to the Austrian military intelligence.

[7][8] The Czech Ministry of the Interior and the Swedish Security Service have both acknowledged the use of numbers stations by Czechoslovakia for espionage,[9][10][11] with declassified documents proving the same.

It was the centerpiece of a United States federal court espionage trial, following the arrest of the Wasp Network of Cuban spies in 1998.

The FBI testified that they had entered a spy's apartment in 1995, and copied the computer decryption program for the Atención numbers code.

The federal prosecutors alleged that Montes was able to communicate with the Cuban Intelligence Directorate through encoded messages, with instructions being received through "encrypted shortwave transmissions from Cuba".

[21][22] As discovered by the FBI up to 2010, one way that Russian agents of the Illegals Program were receiving instructions was via coded messages on shortwave radio.

[26] It has long been speculated, and was argued in one court case, that these stations operate as a simple and fool-proof method for government agencies to communicate with spies working undercover.

Writing in 2008, Wallace & Melton described how numbers stations could be used in this way for espionage:[28] Evidence to support this theory includes the fact that numbers stations have changed details of their broadcasts or produced special, nonscheduled broadcasts coincident with extraordinary political events, such as the attempted coup of August 1991 in the Soviet Union.

This can take the form of numeric or radio-alphabet "code names" (e.g. "Charlie India Oscar", "250 250 250", "Six-Niner-Zero-Oblique-Five-Four"), characteristic phrases (e.g.

[citation needed] After the prelude, there is usually an announcement of the number of number-groups in the message,[31] the page to be used from the one-time pad, or other pertinent information.

[33] High-frequency radio signals transmitted at relatively low power can travel around the world under ideal propagation conditions – which are affected by local RF noise levels, weather, season, and sunspots – and can then be best received with a properly tuned antenna (of adequate, possibly conspicuous size) and a good receiver.

[citation needed] Application of spectrum analysis to numbers station signals has revealed the presence of data bursts, radioteletype-modulated subcarriers, phase-shifted carriers, and other unusual transmitter modulations like polytones.

[35]) The frequently reported use of high-tech modulations like data bursts, in combination or in sequence with spoken numbers, suggests varying transmissions for differing intelligence operations.

[citation needed] The North Korean foreign language service Voice of Korea began to broadcast on the E03 Lincolnshire Poacher's former frequency, 11545 kHz, in 2006, possibly to deliberately interfere with its propagation.

[39] In October 1990, it was reported that a numbers station had been interfering with communications on 6577 kHz, a frequency used by air traffic in the Caribbean.

The interference was such that on at least one monitored transmission, it blocked the channel entirely and forced the air traffic controller to switch the pilot to an alternative frequency.

She wrote to the World Service Waveguide programme in 1983 complaining that her listening had been spoiled by a female voice reading out numbers in English and asked the announcer what this interference was.

He had consulted the experts at Bush House (BBC World Service headquarters), who declared that the voice was reading out nothing more sinister than snowfall figures for the ski slopes near the listener's home.

[43] Monitoring and chronicling transmissions from numbers stations has been a hobby for shortwave and ham radio enthusiasts from as early as the 1970s.