What Numbers Stations are.
Numbers Stations are radio broadcasts that appear in
the Shortwave bands twenty-four hours a day, on many
different frequencies. They are used to transmit short
text messages. There are three different types of
broadcast; voices reading groups of numbers or pho-
netic letters, Morse transmissions sending groups of
numbers or letters and noise stations, transmitting sev-
eral different types of noise.
What Numbers Stations are not.
Numbers Stations are not licensed in the conventional
sense, and there is no easy to find information on any
aspect of Numbers Stations from the government agen-
cies that are concerned with radio use/misuse. They
are not weather forecasts, or shipping broadcasts.
Anatomy of Numbers Stations transmissions.
In the case of a voice numbers station, there will be
one of several types of introduction, usually starting at
the top or at some whole fraction of the hour. These
introductions can be a single letter of the alphabet
keyed in Morse, or a piece of music played for several
minutes, before a voice, in one of several languages,
begins calling out numbers. The first numbers called
are usually a three digit number. There is then a call to
attention, signaled by the use of the word Attention or
by some other device, such as bells, gongs or tones. A
group count giving the number of message elements
that are to be sent is then transmitted, followed by the
groups which are sets of numbers or phonetically
spoken letters, usually numbering five in each group,
although there are stations that transmit four figure
groups. At the end of the groups, there is sometimes a
repeat of the groups, if not, there is an ending indicator,
either by a spoken end or a repeat of the introduction
music. Morse stations generally do not have music at
the beginnings and endings. The message structure of
Morse transmissions is identical to the structure of
voice transmissions, save that everything is sent in
Morse code. Each of the noise stations is unique. The
one thing that binds them together is the extreme
length of time that the broadcasts are on the air.