HFU HF Underground
Loggings => HF Mystery Signals => Topic started by: TrueNorthSWL on May 14, 2026, 0152 UTC
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FSK signal on 6943/6950 kHz. Periodically changes to 6941.5/6948.5 kHz.
0130 UTC S6 direct
0200 UTC S9
0239 UTC S9+10dB
It sounds like CW, but it isn't. There's no character spacing or recognizeable international Morse.
A second signal on 6963/6970 kHz. Periodically changes to 6961.5/6968.5 kHz.
0230 UTC S4 direct
9 June 2026 0210 UTC S7 direct on 6941.5/6948.5
Bit rate is approx 20 bits/second. It sounds like Morse, but it's not.These are rumored to be Russian navy transmissions. Multiple signals with different signal strengths, that peak at different times, indicates there are multiple transmitter sites.
These signals were on the 40m ham band for months, 100 kHz higher up. I'm hoping they experienced enough interference from hams on 40m to force them to move. Too bad they chose the pirate band.
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Saw this last night and again tonight
2330 - 6943/6950 is coming in with a 25dB SNR and 6963/6970 15dB SNR
15 MAY
0206 - 6941.5/6948.5 a much stronger carrier signal keeps popping up center of those two (jamming?) 6963/6970 still weaker
(https://i.imgur.com/CYi1uPW.jpeg)
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Yes, active now with very strong signals
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Signals are massive from NAm through Europe and into Mid East (Baghdad)
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This is Russian military (generally believed to be Navy) wide FSK. 7 kHz shift, 20 baud, encrypted, and should be working on two frequency pairs, switching back and forth between the pairs every few minutes.
This signal has been active off and on in 40 meters for at least a couple of years, but this is the first time I have seen it in 43 meters.
T!
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This is Russian military (generally believed to be Navy) wide FSK. 7 kHz shift, 20 baud, encrypted, and should be working on two frequency pairs, switching back and forth between the pairs every few minutes.
This signal has been active off and on in 40 meters for at least a couple of years, but this is the first time I have seen it in 43 meters.
T!
I first noticed these signals about 4-5 months or so ago. There were two pairs of frequencies, and as you said, they would shift from one pair to another pair about every 20-20 minutes (I didn't time it, but it was about that long).
One evening I heard two pair simultaneously -- in the CW section of the 40M band -- one pair much louder than the other. And I'm in WA state.
I also heard them this morning (the morning of the 14th, around 1350 UTC Thursday) on 6964 and 6971 kHz. Very weak, just above the static level.
So they appear to have moved south of the CW section of the 40M band, for whatever reason.
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I'm hearing the pair here as well. Tonight the signals are a bit stronger than last night.
2320 - I'm hearing the signal pairs on 6941.5/6948.5 khz and 6963/6970 khz
2322 - Just now the pair on 6963/6970 QSY'ed to 6943/6950 and the 6941.5/6948.5 pair QSY'ed to 6961.5/6968.5
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In doing some more research, the signals are present again tonight. Really strong in Australia and Thailand. I was looking at different SDRs are around the globe and both of the SDRs in Australia & Thailand have a S20+ signal. So maybe it's originating from the SE?
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I think there is one transmitter in the Black Sea region somewhere (it's been reported as originating from the Crimea, and another SWL on Reddit thinks it may be in the Caucasus), and I also think there may be another transmitter in the Russian Far East.
This is because one morning I heard one pair of frequencies really weak, and another pair of frequencies at S3-4 out of 5, which is too strong for anything from the Crimea or Caucasus to reach the PNW where my QTH, WA state, is located.
I have no other evidence to go on but just what I've been hearing on my radios. I don't usually use online SDR's.
It would be interesting to see if there's any more evidence of two separate transmitters. If it's Russian Navy, one would think that they'd have a second transmitter for the Pacific Fleet -- but I'm just speculating here.
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Is anyone still hearing this signal?
I have not heard this signal for a couple of weeks. Last report on HFU is July 4.
I'm hoping Ukraine knocked out the transmitter in Crimea or its power source.