There are two kinds of dedicated radio listeners. Most are those who listen regularly to their FM or AM station of choice, or to a station that only broadcasts on the internet. The rest are dedicated to other frequency scales: high frequency (also known as shortwave), followed by very high frequency and, after that, the ultra high frequency range, which includes police scanner talk and even satellite signals. Shortwave listeners encounter a world of mostly international radio stations broadcasting from countries like China, Cuba, Iran, or Romania. These frequencies also include amateur radio and marine and air traffic.
Sooner or later, however, those who listen to these more off-beat signals will stumble across strange broadcasts repeating number groups in digitally synthesized voices. Sometimes they are read live, sometimes in Morse code, and sometimes by means of digital noise transmission. These are the so-called numbers stations.
Numbers stations have been in existence since World War I. Over the years they have attracted sporadic interest from journalists, video game designers, and filmmakers. Despite this attention, there are few explanations of what these signals actually are. Too often, they are described as “spooky,” “creepy,” or “mysterious,” and the discussion stops there. It may be disappointing to some, but these stations are not signals from aliens or mind control devices, nor are they dead relics of the Cold War — rather, these stations are part of the sophisticated work of intelligence agencies and militaries, and they are very much still on the air. This article will explain what they are, how to listen to them, and why they matter.
What Are Numbers Stations and Why Are They Used?
Cryptography, the science of encrypting text and data, has been around since the times of Caesar. Before the invention of radio, secret messages could be conveyed in coded letters or through light signals. In the 19th century, transmission along electric lines became possible, first with the telegraph and then with the telephone. Radio was invented at the turn of the century and was quickly put to military use, as the world learned when German interception of the Russian Army’s transmission of orders “in the clear” helped the Germans win a crushing victory in East Prussia in 1914.
The first use of coded numbers broadcasts was during the last years of World War I, when they were sent in Morse code in Low and Medium wave frequencies. Shortwave came into use in the early 1920s and has been used to send encrypted messages since then. When directed at the ionosphere at an angle, shortwave signals reflect back down to Earth at great distances beyond the horizon. This is handy for intelligence operations in foreign countries, or for the military to send orders to faraway units.