Even though they do not operate on any fixed schedule or frequencies known to the public, numbers stations are really very easy to hear. Just tune outside the established shortwave broadcasting or ham radio bands and you'll hear several with patient tuning. While numbers stations can be heard any time on any frequencies, most seem to be heard in North America during the evening and night hours on frequencies from 3 to 12 MHz.
Most numbers stations heard in North America transmit in Spanish. Other languages often heard include English, German, and scattered other languages such as Chinese and Russian. Almost all will use a woman's voice, although on rare occasions a man's voice might be used. You will quickly notice that the numbers you hear sound much like the "intercept" messages used by telephone companies to give out new numbers when you dial a discontinued number, and a similar technology is obviously in use to generate numbers messages.
Five-digit Spanish stations are the most frequently heard variety. They begin transmissions with something like "atención 341 67" repeated for several minutes. The three-digit group is believed to the identifier of the recipient of the message, while the second number is the number of five-digit groups in the message. Sometimes as many as three different messages may be sent in the same transmission. Transmissions usually conclude with the words "fínal, fínal." Almost all of these stations use AM.
What is your opinion ?
