The Secret Shortwave Spectrum

The information presented in this section is for entertainment/educational/research purposes only and does not disclose any information not already available in the public domain.

There used to be an image here, but it has disappeared from the internet.

A slightly creepy phenomenon

Twisting the dial of your shortwave radio, you come across the most "experimental" sounding station you've ever heard. A glockenspiel tune is followed by the voice of a little girl speaking numbers and letters in what sounds like a random order. A techno DJ's pirate radio remix? Performance art? No, you've stumbled across a "numbers station," and the message inside the madness just wasn't meant for you. Somewhere in the world, a government spook, maybe CIA, MI6 or Mossad, is furiously scrawling down the numbers on a pad, a decoding key open at his side. Meanwhile, for the last 30 years an altogether more curious kind of international stations has been noted on the airwaves.

The intrigue of listening to so-called “numbers stations” is, for many, a hobby within a hobby. While some espionage-buffs may be aware of these stations, having experience in radio is a great help in catching the signals. Here, we can determine two layers of interest. First, these transmissions are made (except for a very few) within the shortwave band, which was once an area of technological discovery where radio was developed and used in the early and mid 20th century. Most people today, particularly those in developed countries, consider shortwave radio a dinosaur and many would not even be able to identify where the band is on the radio spectrum. Indeed, the popularity of shortwave has been paved-over with FM radio, internet radio, satellites, and other new technologies. Shortwave offers low-quality and inconsistent reception of far away stations, which simply turns most people off. The others, known as SWLs (ShortWave Listeners) and DXers (DX = Distance) enjoy shortwave radio for its content. SWLs can vary from the listener who grew up with shortwave and enjoys the nostalgia of AM radio to the hard core DXer trying to catch the elusive signal from half a world away. Second, numbers stations provide very little to the average SWLer and DXer. The content of broadcasts are a mechanized voice reading lists of seemingly random numbers, which are very unentertaining to the person tuning around for Latino music or the BBC world service.

The DXer would quickly realize that these stations do not identify themselves, say who runs them, where the transmitter is, or give any relevant information. Although both audiences may listen for a minute, simply because it’s an odd signal, the SWLer will quickly become tired of it and the DXer will not be able to determine the distance of his/ her catch, so both will tune away from numbers stations then and in the future, most of the time. While we have eliminated a vast majority of the world’s radio listening public, there are those who actively listen to these mysterious signals. Many have had an existing interest in espionage that led them to the shortwave band, for many others, it seems, the situation is reversed. The mystery is what attracts them and keeps them, the who, what, where and why.

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"spectrogram of decoded sounds from a Russian selcall system"

So what are these “numbers stations”? Most of the time, the description is in the name. Throughout the globe, one, or several organizations are spending money to maintain shortwave transmissions that transmit lists of numbers in any number of languages to who-knows-who. The voice is normally computer generated, using either gender, and a number of languages including English, German, Spanish, French, Yiddish, Czech, Italian, Portuguese, Arabic, Russian, and Mandarin (Chinese). The formats vary by the station, some open with a number being repeated, others with tones, and still others with an entire song or anthem. The transmissions can occur anywhere in the shortwave band, from 1.7 to 30 MHz, at any time of the day. Most occur between 4 and 12 MHz during the local evening hours, from five to fifty minutes in length, usually beginning on or near the top of the hour. Some stations use morse code instead of verbal numbers, others use the phonetic alphabet (alpha, bravo, charlie…), still others simply transmit cryptic strings of letters in morse code (example: SHFWO, TIFDK, FISKE…).

These stations are usually just outside of the standard shortwave bands, where normal stations cluster, so try there first. Remember to use the internet and other resources to find out who caught what recently, this may help you find a future broadcast. When listening to a numbers transmission, or an eerie noise, or some other artificial phenomenon on the shortwave band, a cold chill might go up your spine. It’s the intrigue that drives the SWLer to listen, perhaps copy text, and determine new patterns by watching old ones. Who is transmitting it? Who is receiving it? How is the message encoded? These messages may be “dummy traffic” or it may be preventing world war from happening next week, the numbers listener does not know which, but finds the question fascinating.

Just keep in mind that when ever your tuning around on any of the GlobalTuners receivers. Hearing some strange unidentifyd transmission ? There's a good change you just have encounterd one of the most mysteriues things that are on these  mysterious HF airwaves.

Issued by Pascal.

For GlobalTuners