The stations I am referring to are the Single-Letter High Frequency Markers (SLHFM's), also known as channel markers. These are stations that repeat a single letter of Morse code endlessly on a given frequency. On the 7th of December 1998 I found a D channel marker on 6550 kHz. It appeared there continuously for several days, but is now quiet.
Channel markers have been noted all over the HF spectrum for nearly thirty years or so. They were quite active in the 1980's, but their activity decreased markedly by 1990. It is now rare to hear one, although occasionally a few "beacon clusters," or a group of SLHFM's on the same frequency, can be heard. Most of these stations were operated by the Russian navy and used to mark a frequency for RTTY transmissions.
When listening to a channel marker, sometimes the CW marker will be interrupted by a few 5F CW numbers and a RTTY transmission. At the end of the RTTY transmission, the CW marker returns. An example of this is a P channel marker I heard on 21 May 1992 at 0140 on 3732. The P stopped and was replaced by "UMS UMS UMS," then 09728 82828 sent three times, and then into RTTY. Unfortunately I didn't have a RTTY decoder at the time so I can't tell you what the baud & shift was, or if it was encrypted or not. I believe others have decoded RTTY sent by these stations and it consisted of 5F groups. UMS is a callsign allocated to the Russian Navy in Moscow, although the station may or may not have been located in Moscow. Unfortunately, I didn't hear any RTTY from the recent D marker on 6550.
The beacon clusters that I mentioned earlier most likely have a different purpose. According to an article written by M. G. in the ENIGMA newsletter issue 14, these clusters are most likely propagation beacons as opposed to channel markers. I tend to agree with this. As far as can be determined, there have never been any RTTY transmissions from the SLHFM's that are grouped in clusters. These stations are too close together in frequency to be of any use marking channels used for RTTY transmissions. The beacon clusters are most often heard in Europe, although occasionally a group can be heard in North America on 7028 kHz, in the 40 meter amateur band. I used to hear a cluster group there often while in Europe, normally consisting of a C, D, and S beacon. Each letter was sent at a different speed & pitch.
The most active SLHFM's as of late are a couple of P markers I logged in 1993, an L marker with a chirpy transmitter on 3094.5, a few cluster beacons on 7028, and the recent D marker heard on 6550. As I have said, it is rare to hear one, especially in North America, so any time you hear one it's a good catch.
Some channel markers have been traced to different locations inside Russia. This list was provided by Rick Baker:
C Moscow
F Vladivostok
L St. Petersburg
P Kaliningrad
R Ustinov
S Arkhangelsk
V Khiva
Something new that I want to do for 1999 is include your loggings here every month. If you would like to have yours included, just send them to me at my email or snail mail address at the top of the page. Just use the normal format of including frequency, time, mode, and type of station. You may remain anonymous if you wish. Your station logs and information is much appreciated.