What in the world is this - broadband digital?

Duane_AC5AA

Last night on the low end of 17m there was a relatively strong "correlated noise" signal that had all the earmarks of some kind of broadband mess.  Since appears to be an interloper on 17m, I'm just wondering if anyone recognizes the panadaptor/waterfall view.  Listening to any particular part of the signal just sounded like noise, but a look at the waterfall seems to indicate something else going on.  

Stu Phillips - K6TU

Duane,

It looks like a signature typical of Over the horizon radar that has been seen on many of the HF bands - especially on 20m and 15m - the pattern you are seeing is because of Rayleigh scattering in the ionosphere.

One way to confirm is to measure the pulse repetition rate by recording the audio in Audacity or similar and measuring the time between noise spikes.

The other reported versions of OTHR on the HF bands that fit this bandwidth are believed to be from the Middle East...

Stu K6TU

Duane_AC5AA

Thanks, Stu.
 
    73, Duane  AC5AA

Ken - NM9P

If you turn the Weighted Averaging ON on your display tab and the panadapter rises dramatically, then it is a good indication that you have a signal with very short, rapidly rising pulses, which is another indication of OTH radar.  I have seen the peaks rise by a factor of about 8 or 10 over the same panadapter trace with Weighted Averaging turned OFF.

Ken - NM9P

Duane_AC5AA

Thanks, guys - the last obnoxious OTHR I dealt with was the infamous Woodpecker, and that was nasty.  This shut off, at least on these particular frequencies, just after I took the screenshot above.  It was impossible to hear a weak signal under the noise it created.

Martin AA6E

Duane,

To me, it looks like a typical digital modulated signal, like those you can find at various frequencies.  Here is an example I can find at 16.9 MHz.
These are two transmissions, each 2 kHz wide.  (Yours is unusual because it is 20 kHz wide.) The transmissions start out as essentially white noise with flat spectra.  The structure you see in the waterfall is ionospheric scintillation, caused by the signal bouncing off moving clouds of charged particles in the ionosphere.  (It's what we used to call selective fading in the old pre-panadaptor days.)  The details of the pattern and drift rate will be different depending on frequency, path length, and ionospheric conditions.

So your signal could have been somebody's hi-tech radar, but I think it's likely to have been a wideband digital communications channel.  DRM broadcast stations will show interesting patterns like these, too.

There's all kinds of weird stuff out there on HF, and the Flex is just the radio to view it!

73 Martin AA6E

Duane_AC5AA

That's interesting, Martin. I also note on mine that there are two "marker" signals, one at each side of the bandspread of the signal.  I'm not sure if those are the same on your example or not.  I've seem some very interesting 3-5 KHz wide signals in the ham bands (usually they are 3 KHz, but some have been wider) that may be Pactor 4 (?) or something - interesting to watch, awful to be underneath if one opened up on top of a QSO!  Anyway, you're right, the Flex panadaptor/waterfall really brings the radio alive again for me.  The first "video" gadget that did this for me was the "Magic Eye" tuning on my uncle's Zenith radio (and later on a Gonset Communicator!)....

   73, Duane

Walt - KZ1F

ionospheric scintillation?

Martin, you just earned your 2x1 (again)! That's good, an excellent diagnostic on that. And I've been shamefully thrilled other people are seeing that stuff besides myself. I was beginning to think it was me, either interior noise or exterior noise.

Ed_NZ1Q

I've seen the same signal, 20 kHz wide on 20m. That was just a few days ago, around the same time Duane saw the pic he posted.  It came and went but was on top of the PSK and JT segments at 14.070 and 14.076.

Richard Simpson

3khz wide in hambands is probably Digital Audio - perfectly legal. 20khz, probably not.

Rick
K3IND
Still loving my 1500