Strange data (?) signal on 6860 kHz

[WA4FHY]

I usually park on 6925 kHz if I'm not doing anything else; one afternoon last year,
just before Thanksgiving, I started seeing a strong carrier on 6860 kHz. It was of
interest because it was much stronger than any other signals in that part of the band -
 see screenshot below (I hope!). The signal would come on near local sunrise, NOT fade
in but as if someone flipped a switch; it was of more or less stable strength until around
sunset when it would go away just as it appeared in the morning - as if someone
flipped a switch off. One day I decided to see if it was a real signal: 1) fired up the trusty
ol' R-70 and yes, it was there, 2) I logged onto several remote SDRs, from the Northeast to
Point Reyes, with a stop at the Northern Utah SDR - it could be received on all of them. 




Shortly after the first of this year, I noticed a change - I could see what looked like modulation
that seemed to be near random bursts of data. See image below. Also, it did not show up
as regular as in the past.


More recently, it has changed again - the carrier is gone, only the random data bursts
show up! See image below.


This has my curiosity; I have no idea what this is. Any thoughts on this anyone???

10may21 - Looks like the same, or similar, station is using 6885 kHz this morning.

19sep21 - This, or similar, station is now sometimes on 6860 kHz, 6885 kHz, or 6988 kHz
                 Seems to change with time of day. Also, "data bursts" are not as wide as originally seen

 

[BoomboxDX]

I heard the carrier earlier this morning (Sept. 15, 2025) on 6988 kHz between 1135 UTC (when I tuned in) until 1150 UTC when it switched off. It was weak, under S1 in signal strength, and had a polar flutter to it.

This was on my Tecsun PL-330 and an 8 meter indoor wire, and I'm in the PNW US.

I suppose I'll have to monitor this frequency more often.

[BoomboxDX]

I heard the signal again early this a.m., Pacific time (Sept 16th, UTC), from tune in at 1229 UTC until it cut off completely at 1309 UTC, which was 6:09 a.m. Pacific Time. Frequency was 6988 kHz. The signal seemed to increase in strength from 1229 to 1300 or so, from around S1 out of 5 to S3 out of 5, before seeming to dip again right before cut off.

The signal also -- just like last time -- had what sounded like a polar flutter or fast fade to it, maybe 6-10 fades per second. Cut off was the same as I described and WA4FHY has described. Like flipping a switch.

Unfortunately, neither time I've heard this carrier have conditions or activity on 40M been good enough to judge the 6988 kHz signal against anything else. Both times I did NOT hear the Petropavlovsk 'K' beacon on 7039, which usually is a pretty good beacon to N Asia and the N Pacific. But, as we all know, prop can vary from region to region. Still, this signal stuck out when there was no DX activity, to speak of, in the lower reaches of the 40M band (CW was dead).

Being that this signal is a bit erratic, and that the increase in signal might have been due to a grey line effect (indicating it might be in the US), I wonder if this is a pirate signal of some sort. Especially considering the proximity to the pirate radio frequencies.

Just throwing that out there. At this point, I have no idea what the signal may be.

This time I tuned it in on my DX-394, using my indoor wire.