Yesterday, I was playing with WebSDR, an awesome software defined radio that you can access from the web, and I noticed that there was a Morse signal on the 40m band that just repeated “D” endlessly, and right next door, another that repeated “C” endlessly. A bit of digging revealed that these were “letter beacons”, transmitting from the Soviet Union Russia. (Man, I’m dating myself by accidently calling it the Soviet Union.) Neat, think I. They all appear clustered around 7.039 or so on the 40m band, so I bet that lots of radio amateurs have heard them all the time. Anyway, here is the Wikipedia link.

Letter beacon – Wikipedia, the free encyclopedia

But this morning, I was having a little breakfast and turned on the radio. For kicks, I dialed down to that portion of the band, and, oddly enough, could hear “dah dit dah” and “dah dah” repeating. Wow, those are beacons “K” and “M”. Here’s a picture of what the signals look like through my spectrogram code:

Here is a link to the MP3 recording I made. As I am editing this post, I am continuing to listen to the live radio. I can still hear M pretty clearly, but K has been fading in and out, and now I can’t hear it very often.

I’ll probably work out the distances to these transmitters later. According to my calculations, the K signal is at about 7.039315Mhz, and the M signal, about 7.039415Mhz, 100hz higher. The Wikipedia doesn’t list a 40m frequency for K, but it lists 7.0394 as being a frequency for M, so I’m pretty close.

Addendum: According to Wikipedia, the K beacon is in Petropavlovsk-Kamchatsky, which works out to grid QO59jn, and M is in Magadan, in grid QO93ha. Running my grid program, I get bearings of 313.4 degrees and 322.5 degrees, respectively, at distances of 3755 and 3903 miles.

Addendum²: It’s now the next morning. I can hear K and M again around 7.039, so I guess that isn’t that difficult. I tuned upo around 10.8725, and found M broadcasting there, a bit more difficult to find, but it’s pretty clear. Here’s the spectrogram:

Addendum³: It’s a couple of mornings later, and I’m still hearing them. My guess is that I’m getting so-called “gray line” propagation from northern Russia, but I should really plot that out on the map. This morning, I decided to try to make the beacons more obvious by plotting their intensity using a logarithmic scale. Maybe it’s better, maybe it’s not.