Russian Cluster Beacons (MX)

These CW signals are from the famous single-letter beacons, variously referred to as SLB, SLHFB, SLHFM, and of course ENIGMA's designator of MX (Morse code oddity).

In particular, we're looking at the 40 meter cluster around 7039 kHz. I'm not altogether sure it really should be using this part of 40, but in any event it is, and at this time around 0700 UTC in early 2009, it was doing much better than usual here in California.

A look at the frequency scale gives an immediate idea of the structure of this and the other clusters. "C" (Moscow) is always on the even kHz, with the other letters always offset by the same amount. Uneven fading and other characteristics prove that these transmitters are not all in the same place. It is widely assumed that this and the other clusters spaced all through HF are used by the Russian military for propagation checking.

Reading up from the bottom, we see "D" (Sevastopol?) on 7038.7 kHz, "P" (Kaliningrad) on 7038.8, "S" (Severomorsk) on 7038.9, "C" (Moscow) on 7039.0, and "A" (Astrakhan?) on 7039.1. "F" (Vladivostok), "K" (Kamchatskiy), and "M" (Magadan) were not heard.

Plot made with Spectrum Lab.