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.

[BoomboxDX]

I heard a similar carrier on a different frequency this a.m., on 6938, tuning in at 0525 UTC. It varied in strength from S1- to S2+, peaking around S4 around 0600 or so, probably a short, strong fadeup.

It was still on when I checked it later, around 1135 UTC (0435 a.m. Pacific Time). Next time I checked my DX-394, at around 1300 UTC, it was off.

Once again, there was little to zero activity on 40M to compare it with. The Petropavlovsk 'K' beacon was in with some moderately strong signals, on 7039. The San Francisco ACARS / HFDL digital bursts and beeps were blasting away on 6559 kHz. But nothing else, really, to compare this unid. signal with. The unid. Stanag transmission on 6843 kHz was no help, really, as no one seems to know where that is located. NAU's FSK was loud out of Puerto Rico on 6487.

Of course, if this unid carrier is low power, comparing it to other known stations really is an exercise in futility.

[BoomboxDX]

Lately I've logged these mystery carriers on 6988, 6938, 7000, and 6979 (0908 UTC, 3 Nov). On at least one night (0709 UTC 31 Oct) I noticed two carriers, one on 7000 kHz and another on 6938 kHz, both at roughly the same strength.

Just three hours ago (0951 UTC, 5 Nov) I logged one on 6900. Being that the remainder of the 40M spectrum was basically dead (i.e., nothing out of Japan, 'K' beacon from Petropavlovsk missing), I still think the mystery carrier was somewhere in the Western US.

The carriers seem similar, but then again, a carrier is a carrier, right? So it's possible they have no connection. That said, they seem to appear during the same hours, and have no other components, at least that I've heard (the OP's noticing data bursts notwithstanding).

I've noticed these dead carriers always having the same general strength from night to night, depending on the general propagation for the band. It reinforces my guess that they are from the western US somewhere, as the propagation from these carriers doesn't seem to match anything coming out of Asia or Siberia, unless the carriers are super high powered.

[Token]

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.

This signal is an HFT (High Frequency Trading) related waveform.  Yes, I know, everything gets blamed on HFT.  But, this one specifically is license holder WP2XCZ, RCA Telecom LLC.

The signal should come up on frequency with a Morse ID at the beginning of each transmission, and then ID, with Morse, every 20 or 30 minutes after that.  WP2XCZ (and several other HFT experimenters) started IDing late last year, after they lost an FCC granted "ID exemption" that they had been operating under for some time.

T!

[BoomboxDX]

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.

This signal is an HFT (High Frequency Trading) related waveform.  Yes, I know, everything gets blamed on HFT.  But, this one specifically is license holder WP2XCZ, RCA Telecom LLC.

The signal should come up on frequency with a Morse ID at the beginning of each transmission, and then ID, with Morse, every 20 or 30 minutes after that.  WP2XCZ (and several other HFT experimenters) started IDing late last year, after they lost an FCC granted "ID exemption" that they had been operating under for some time.

T!

Just curious, to your knowledge do these HFT transmitters run dead carriers when not sending data? I've heard of some transmitters in the Ute spectrum transmitting dead carriers as a sort of guard frequency. Would these HFT stations do the same thing?

I haven't yet read that HFT stations send dead carriers when not transmitting data.

Also, are most of these HFT data transmitters in the Midwest? If so, they must be putting out the watts to slam a PL-330 on an indoor antenna here in WA state where I live.

[Token]

Just curious, to your knowledge do these HFT transmitters run dead carriers when not sending data? I've heard of some transmitters in the Ute spectrum transmitting dead carriers as a sort of guard frequency. Would these HFT stations do the same thing?

I haven't yet read that HFT stations send dead carriers when not transmitting data.

Also, are most of these HFT data transmitters in the Midwest? If so, they must be putting out the watts to slam a PL-330 on an indoor antenna here in WA state where I live.

I do not know, first hand, anything about these stations.  But I have intentionally observed them quite a bit.  So my understanding is strictly limited to what I have seen.

In general, I have not seen HFT stations use a dead carrier when not sending data.  The exception to that is this particular station / format in this thread.  The carrier with wideband pips / PSK data every second or so.  On several occasions I have seen it be a dead carrier for extended periods, either after a period of the pips or before the data starts.

The "center" of the HFT stuff seems to be in the Chicago area, however there are also sources in Europe, as well as the PNW (Washington, licensees such as this specific signal in this thread, WP2XCZ, Ritzville, WA) and in Canada.  I believe there are some stations in the Northeast also, NY / MA area, but I have not yet tied those to a specific license.

As for them running some power, yes, they do.  According to their license information, this particular station has an ERP, on this frequency, of over 400 kW, and some frequencies are more like 900 kW (TX power is 16 kW).

T!