Numbers stations are simply shortwave radio transmitters usually operating between 3,000 and 30,000 kilohertz and are possibly pirate stations which operate unlicensed leaving them absent from any government documents. If they are not pirates, then who is authorizing them? If they are pirates, then what audience are they transmitting for? Using Short Wave radios will never arouse any suspicion unlike the use of more sophisticated computer equipment.
The broadcasts generally begin with an alert signal which may be a simple tone, or it can be fragments of a song, such as with the famous Lincolnshire Poacher station, which begins broadcasts by playing several bars from the well-known tune of the same name. Others include Magnetic Fields (Jean Michel Jarre), Swedish Rhapsody, Cherry Ripe. This indicates to listeners that a message is about to begin.
Number stations use a system which is absolutely secure. A so called ‘One Time Pad’ provides the key for encryption and decryption using a string of numbers as the key. After use the code is destroyed meaning that no part of the key is ever reused.
Not all Numbers stations send out simple numbers. Some of them send out noises instead. The station known as ‘The Buzzer’ sends out high precision buzzing on 4625khz 24 hours a day, every day of the year. It has been on the air for over 10 years with no information about its source.
Here is an example from the Swedish Rhapsody station
