If you have listened to shortwave broadcasts or utility stations, you will no doubt have run across the “numbers stations.” Wikipedia says,
Numbers stations (or Number stations) are shortwave radio stations of uncertain origin. They generally broadcast artificially generated voices reading streams of numbers, words, letters (sometimes using a spelling alphabet), tunes or Morse code. They are in a wide variety of languages and the voices are usually women’s, though sometimes men’s or children’s voices are used.
Evidence supports popular assumptions that the broadcasts are used to send messages to spies. This usage has not been publicly acknowledged by any government that may operate a numbers station, but in one case, Cuban numbers station espionage has been publicly prosecuted in a United States federal court.
Last night, I was tuning around the 80m CW band and came across a strong signal on 3528.5 kHz and copied the folllowing ABOUT 2300Z:
QFWNX OLJFL XYNQD ZDVLX OBOZM OOXWO
BRHSH RZFMB KIALN JQMNF CMUCB ZYREI
TLHAR TZTXR YWCXJ ….. ….. …..
This kind of random-letter group continued for as long as I listened.
It was kind of amusing, but a little disconcerting that this kind of operation was right in the middle of a ham band. Google “numbers stations” for links to a whole bunch of sites that speculate about the origins and utility of these stations.
Hamilton says
If your spacing into groups of five letters is what you heard, that corresponds with a memory from my crypto class at Texas A&M that cyphertext is sent in groups of five letters in some cyphers. Kind of cool stuff! For anyone interested, here’s the frequency distribution from the sample, (useful if it’s a simple substitution cypher):
Q – 2
F – 3
W – 3
N – 4
X – 5
O – 5
L – 4
J – 3
D – 2
Z – 5
V – 1
B – 4
M – 4
R – 4
H – 3
K – 1
I – 2
A – 2
C – 3
U – 1
E – 1
T – 3