Welcome to number stations.

What are number stations?

Number stations are high frequency or shortwave radio stations that broadcast a call sign usually music or letters from the phonic alphabet then strings of numbers usual in groups of five numbers.

These broadcasts usually start on or around the beginning of each hour.

Officially the purpose of these stations is un known however it is believe that number stations are one way that intelligence agencies contact there operatives in the field.

Number stations can be heard any time of the day or night on the high a medium frequency bands usually between 2 and 25 MHZ and can be heard in the “utility” bans and on the edge of the international broadcast bands.

These stations are broadcast by many agencies in many languages and from many locations around the world.

They are unlicensed and often cause interference to legitimate radio users.

For example if you listen to Shannon Volmet on 3.413 KHz USB at the top of most hours in local hours of darkness you will hear a woman reading letters from the phonic alphabet.

This broadcast is actually on 3.415 KHz AM and is believed to be broadcast from Israel .

History of number stations

Number stations are believed to have started on of around the time of the First World War. They have certainly bee around since the start of the cold war.

Number stations are believed to have started in CW mode (Morse code) but by the arrival of the cold war they were mostly voice in AM. May are now moving to single side band (SSB).

Originally numbers were hand keyed or used recording of real people. This carried on until the around the mid 1980s when recordings were replaced by automated or computerised voices like the ones used by telephone services.

Number stations were at there most active during the cold war. Number station activity today is about a one third of cold war.

This could lend credibility to the espionage link.

How does it work?

At the spy HQ a message to an agent is encrypted using a cryptography key called a one time pad. This key is a dictionary for a language that is only used one.

The message is then broadcast according to a pre set schedule possibly from an embassy or military base located in another country.

An agent in the field has is issued a shortwave radio (probably a portable something inconspicuous), a copy of the schedule a book containing copies of the one time pads he will need.

The agent then listens at a time and on a frequency listed on his schedule

He listens to the message header to see if the message is for him and what key to use.

If the message is for him he notes down or records the number and then uses his key to decode the message. He then destroys the key.

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