The most basic definition of a spy numbers station is a station broadcasting groups of numbers read by a male (OM) or female (YL) voice on the high-frequency (HF) bands. Of course, there are also a large number of Morse code (CW) and radioteletype (RTTY) numbers stations as well.

A typical numbers broadcast begins with a callup of some sort. This is usually a number that is repeated for several minutes, but some other identifier and even music can be part of the callup. The purpose of the callup is to allow the recipient (agent) find the frequency the station is using. After the callup, sometimes a message preamble is sent. This may consist of the message number and group count. After the preamble, the message groups are sent. These are usually sent as four-figure (4F), five-figure (5F), or 3/2 figure (five numbers with a pause between the third and fourth number, e.g. 123 45) number groups, hence the term "numbers station." The message groups can either be repeated or the whole message itself repeated. After the message, some sort of signdown is usually sent, whether this is a simple AR or a repeat of the message preamble. Of course, this is just a generalization, and there will be a wide variety of formats used. Also, letter groups are sometimes sent instead of numbers.

You won't find these stations listed in any shortwave broadcast guide or listed with the ITU. The agencies behind these operations want to keep them as low-key as possible. Normally, no callsigns are used, although there have been exceptions. You also won't be getting any QSL's from these stations (again, there is one exception - more on this in a future column!)

What are numbers stations used for? They are used to transmit messages to intelligence agents located in foreign countries. It is a very simple matter to receive a numbers broadcast on a cheap, portable shortwave receiver. Such a radio would attract very little attention to someone traveling abroad compared to a room full of high-tech communications gear. Also, it is nearly impossible to track who may be receiving numbers stations. Another benefit is that the messages themselves are completely secure. They are decoded by the receiving agent with what is known as a "one-time pad." This is a pad with a number (say, five-figure), on each page. The number groups of the message are either added to or subtracted from the current day's number, without carrying any numbers. The resulting 5F number would be looked up in a code book to find the translation.

So, with that introduction, I hope you are now interested in chasing numbers stations. For further information, the following books are good reading:

Uno, Dos, Cuatro by the late Havana Moon
How To Tune the Secret Shortwave Spectrum by Harry Helms
Underground Frequency Guide, 3rd edition by Don Schimmel
Secret Signals, The Euronumbers Mystery by Simon Mason

If you have internet access, check out these websites:
www.access.digex.net/~cps/numbers.html www.ibmpcug.co.uk/~irdial/enigma.htm

Also check the "Communications Confidential" column by Rick Baker in Popular Communications, and "Utility World" by Larry Van Horn in Monitoring Times for loggings of numbers stations.

For those of you that want to get started right away, check the following frequencies:

8300 - YL/Chinese "New Star" station. Usually can be heard very weakly around 1200 UTC at my location, but those on the west coast may have better luck hearing it.

4645/4670 - YL/EE CIA "Counting Station" has been active at 0100 lately.

For the Cuban YL/SS stations, check the following frequencies: 3292, 4017, 4028, 4479, 4507, 5417, 5903, 6286, 6768, 6786, 6797, 6855, 6983, 7482, 7583, 7726, 7890, 8012, 8086, 8186, 8906, 8970, & 9063. A sked for this station will be in a later column. Check these freqs in the evening hours. Transmissions usually start at the top of the hour. It's fun to watch these for mistakes.

I hope this gives you an insight as to what this numbers station business is all about. This is by no means a complete list of all numbers stations, but was meant as an introduction to numbers station listening. Let me know what you find.