27 July 2014

Cluster Beacons

(a.k.a. Single Letter Beacons, Single Letter High Frequency Beacons or Channel Markers)

"D" and "C" cluster beacons
Letter beacons are radio transmissions of uncertain origin and unknown purpose, consisting of only a single repeating Morse code letter. They have been classified into a number of groups according to transmission code and frequency, and it is supposed that the source for most of them is Russia.  Letter beacons have been referred to as:

    SLB, or "Single Letter Beacons"
    SLHFB, or "Single Letter High Frequency Beacons"
    SLHFM, or "Single Letter High Frequency Markers"
    Cluster beacons
    MX (a more appropriate ENIGMA and ENIGMA-2000 designation)

The purpose of the letter beacons is not yet known with certainty. Many theories have appeared in specialized publications, but none is based on documentary evidence. They have been postulated to be radio propagation beacons, channel markers, or beacons used in tracking satellites or for civil defense purposes.[9] Some stations of this family, in particular the “U” beacon, have been implicated in deliberate jamming. According to ENIGMA, cluster beacons are used by the Russian navy (especially its submarine branch) to find the most suitable radio frequency for contact based on current radio propagation conditions.
A recent source (2006) regarding locations was published on the Web by Ary Boender (UDXF). This publication also contains an extensive list of letter beacon frequencies, both current and historical.

A short summary from Numbers & Oddities MX file is added here.

"Numbers & Oddities" a.k.a. the "Spooks Newsletter" is a newsletter for the members of the Utility DXers Forum (UDXF), the Spooks mailing list, HF Underground and everyone else who is interested in Numbers Stations. "Numbers & Oddities" covers the fascinating world of Numbers Stations and all kinds of other odd signals on HF.

The beacons are on the air since the late 1960s. Until the late 1980's these beacons could be heard on numerous frequencies throughout the SW spectrum. After the disintegration of the Soviet Union, many of them disappeared and only a few survived. Some of them are very active, especially station "P".
What is their purpose? you might ask. Well, there are a number of theories; amongst them are several weird ones. Some say that they are river beacons, others state that the beacons are in fact UFO homing beacons. One person suggested that the beacons are part of the Russian strategic missiles network. He thinks that the Russians would launch their nuclear missiles when the beacons stop. Well, that certainly is not the case.
It is widely believed that the so called "cluster beacons" are propagation beacons. A Russian naval radio officer told me once that the cluster beacons belong to the Russian Navy. That was the confirmation of a theory that many dxers had for years.
The beacons that we hear today are either propagation beacons or channel markers. 

"Cluster" beacons because they transmit in clusters, groups of frequencies only a kHz apart. The cluster frequencies are 3594, 4558, 5154, 7039, 8495, 10872, 13528, 16332, 20048 kHz. A typical cluster looks like this:
Cluster beacon slots:
.7 "D", Sevastopol
.8 "P", Kaliningrad
.9 "S", Severomorsk
.0 "C", Moscow
.1 "A", Astrakhan
.2 "F", Vladivostok
.3 "K", Petropavlovsk Kamchatskiy
.4 "M", Magadan

Example of a cluster:
"D" - 8494.7
"P" - 8494.8
"S" - 8494.9
"C" - 8495.0
"A" - 8495.1
"F" - 8495.2
"K" - 8495.3
"M" - 8495.4

The majority of the other beacons are channel markers.


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