Protection from missiles: a 120 mm Jamming Round

For the first time I heard these beacons in Morse code around 1970. Many of them are still alive and are regularly observed by many Utility specialists. They were/are operated by the former Sovjet Navy/CIS Navy from several locations. Single-Letter-Channel Markers have used many frequencies in all the years and many are obsolete now, Cluster-Beacons however remained on their frequencies. All Navy beacons sometimes suffer from technical shortcomings, e.g. garbled letters, hum on carrier, etc. Channel Markers often are not spot on frequency.

Ary Boender 1996 published details concerning the purpose of these transmissions;
saying that it is believed, Single-Letter-Beacons are used as Channel Markers to keep a certain frequency free for traffic. Channel Markers quite often work in parallel and at certain times only. We can't predict their operating skeds.
Although assigned to Navy HQ provisional RDF have shown, that transmitters and HQ are not at the same place. "P" on 3291 // 3837 kHz in April 2008 always was received from directions around 90°, Kaliningrad bearings should be around 40°.

Occasional transmissions in Morse code or BEE 36/50 from Navy stations interrupt the continous stream of the same letter with messages mainly to collective Navy callsigns. At rare occasions even voice messages in Russian have been observed.
One example is again Channel Marker "P" on the frequencies 3699.5//3837//3291 kHz,
which quite frequently is interrupted by BEE 36/50 traffic and Morse routine messages from/to RDL and other callsigns.
It is interesting to note, that all BEE 36/50 traffic, so far heard on Channel Marker frequencies, will decode upon the same sync string like on VLF. It is obvious, that a multitude of transmission channels make sure the information will arrive.

The table shows just a small selection of Channel Markers and its origin.

Stations D, P, S, C and A are active

Cluster Beacons are grouped around a centre frequency which always is letter "C" for the Navy Headquarter in Moscow. The frequency slots are 100 Hz apart. One or several slots can be active at the same time. It seems, the Cluster Beacons are on the air at times of increased activities of the Navy (exercises, accidents, etc). Skeds are however not predictable. The purpose of these beacons is not known, nowadays they most probably only serve as propagation indicators. To my knowledge no messages have been heard so far on the frequencies.

The following centre frequencies are frequently used:
3594, 4558, 5154, 7039, 8495, 10872, 13528, 16332 and 20048 kHz.

The slots are assigned as follows:
.7 D Sevastopol UKR
.8 P Kaliningrad RUS
.9 S Severomorsk RUS
.0 C Moscow RUS
.1 A Region of Astrakhan RUS
.2 F Vladivostok RUS
.3 K Petropavlovsk Kamchatskiy RUS
.4 M Magadan RUS

A complete Cluster Beacon consists of:
10871.7 D
10871.8 P
10871.9 S
10872.0 C
10872.1 A
10872.2 F
10872.3 K
10872.4 M

Cluster Beacon on 16332 kHz

This is an example of a distorted transmission. C and S channels are ok, but the third character is garbled and doesn't fit into a 100 Hz slot.


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