HFU HF Underground
Loggings => HF Mystery Signals => Topic started by: BoomboxDX on February 07, 2026, 1609 UTC
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Earlier this a.m. I was tuning the range below 7000 kHz, a section of HF that often has some unusual signals. I don't look for pirates, like many others, but I often hear dead carriers fading up and down for hours, OTHR covering wide swaths between 6800-6900, and the like.
This a.m. I heard very strong digital hash, seemingly centered on 6838, a frequency that I often hear a dead carrier on early mornings here in my section of WA state (usually between 1000 UTC and 1400 UTC or so).
In this case, there was strong digital hash, with pulses embedded, each burst lasting around 30 seconds, with very fast pulses (around 12X a sec.) just before it stopped. There would be a half second of silence, then it would start up again. The range it covered was between 6832 and 6842 kHz. I first noticed it at tune in around 1145 UTC (0345 Pacific local time), and it was still there at 1305 UTC when I switched the radio off.
This was with my Radio Shack 200629 which has a dumb BFO, so the frequency range was probably pretty accurate.
At the same time, there was a dead carrier on 6938, around S3 out of 5, with fading. I am not sure these two are related, but I often hear dead carriers on both of these frequencies during early mornings. I hardly ever hear digital hash on either frequency when I tune in.
On the morning of the 6th UTC, I also heard some digital hash on one of these frequencies, probably 6838 also (I think I mislabelled the frequency in my logbook, it seems that the hash went from 6836 to 6839, loudest around 6836, but that was on a radio with LSB (XHDATA D808), making it harder to find the center frequency, because it changes between USB and LSB.
Both mornings the digital signal was S5 and even S5+, making me wonder where in the world it is located. Conditions to the Far East were fair in the 41M broadcast band, but not awesome. For example, the 'K' beacon from Petropavlovsk on 7039 wasn't coming in, though CRI to Siberia was S4+.
I didn't hear any OTHR this morning, and extremely weak OTHR yesterday morning between 6800-6900, and I think the OTHR may be from Asia somewhere, so it makes this digital signal look as if it could be domestic.
Radios, as I mentioned were a Radio Shack 200629 and XHDATA D808, both with a 25+ foot antenna.