Number stations

If you have a shortwave radio with continuous tuning then you have the ability to listen to frequencies between the standard broadcast and amateur radio bands.

Whilst listening between the regular bands you may sometimes hear something a little odd. Perhaps you will hear a female with a slightly mechanical voice. Instead of reading the news or introducing a piece of music all you will hear from this sultry maiden are numbers or NATO call signs (alpha, bravo, charlie etc).

If you listen over many weeks you will realise there are schedules, set frequencies and a certain style in the reading of the numbers and call signs. You will notice that the voice is emotionless and never falters.

These broadcasts are from Number Stations and they have been broadcasting for decades. Number stations are government security departments sending messages to spies out in the field. The messages are generated electronically hence the monotone voices. There is no lady reading from a script.

You will ask, "Why use an 'old fashioned' technology like shortwave broadcasts when everyone uses the Internet to send messages?" Well, the drawback with the Internet is that you have to go online to read an e-mail and, as soon as you do go online, counter-espionage forces will know exactly where you are. With a shortwave broadcast nobody knows to whom the message is for. The spy may be anywhere within range of the transmitter.

The spy can use a tiny receiver, especially made for the task, to listen to the message. The message is encoded using an unbreakable one-time pad, which uses a never-ending random encryption algorithm that can never be broken. Only the spy in the field can decode the message with his copy of the one-time pad. Number stations offer a clean and efficient way to send messages to spies.

One transmitter has been traced to a British military base on the island of Cyprus. It is believed to be sending messages to people spying for British intelligence in the Middle East. The Lincolnshire Poacher, as the number station is known, broadcasts a piece from the folk song The Lincolnshire Poacher to alert spies that a message is imminent. A message is then sent in groups of five numbers.

Another spy service run by Israel's Mossad sends NATO call-signs in groups of five NATO call-signs to its agents. In Cuba, Spanish messages are sent to spies in the US, Carribean, Central and South America.

If you want to listen to Number Stations then any shortwave radio with continuous tuning and SSB will pick up messages. Don't expect to decode the messages as one-time pads are the only truly unbreakable encryption methods. Number station listening is a hobby in itself and there are a band of dedicated listeners logging messages, transmitter locations and regularity of messages during times of strife.