25 meter band hit by broadband noise, possible jammer

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Token

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Hello all,

For the past 5+ hours the 25 meter band has been hit by broadband noise. This noise is very similar to what might be seen from an PRN or similar radar, but I have not seen such an application in HF before. I have no idea if this signal is unintentional or if it is intentional, I suspect intentional. What its purpose is again I do not know.

The signal is very wide, covering roughly 11250 to 11900 kHz, with it speak around 11610 kHz. It is not a local signal to me, it was first reported on the east coast at around 2150 UTC and at that time I could not detect it at all. As the evening progressed the signal started coming out of the noise for me. Around 0100 UTC it was strong enough to wipe out many broadcast stations in that band. At this time (0320 UTC) it is starting to fade, but still has significant strength.

The signal appears strongest on east coast (USA) remotes but can be detected on European remotes also.

At least twice the signal has paused for a short time, on the order of two to five seconds, once at 0023 UTC and once at 0303 UTC. I have no idea if it did this other times or not, I was not watching it the whole time, those are just the ones I noticed. During the pause the absence of signal makes the total width covered very obvious.

0023 UTC pause:
original.jpg


0303 UTC pause:
original.jpg


Hopefully it goes away soon, and does not become a regular fixture.

T!
 

db76662

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I'm hearing it as well in central North Carolina. At first I thought maybe the unseasonable weather had something to do with it, but I don't think that's the case.

I'm seeing the most heavy interference on COTHEN 11494 KHz USB -- almost sounds like STANAG 4285 -- but it's been continuous since about 2000UTC.
 

Token

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Here in the Mojave Desert of California it came up prior to 2300 tonight (01/13/2013). At this time (0240 UTC, 01/14/2013) it is still up. Tonight it has turned off and on several times, more often than last night. At one point it also stepped down in power about 20 dB without actually going off the air, after several minutes it came back up to full power.

This is a couple of the off/on cycles:
original.jpg


T!
 

mancow

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The fact it's avoiding 11.175 makes you wonder if it's the US testing something.
 

Token

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I don't see any indication tht it is avoiding 11174 kHz. It rolls off in power below 11450 kHz and it is a steady decline until down around 11000 kHz. It does the same thing on the high side starting at about 11900 kHz and going down to about 12200 kHz. The plateau across the top is from about 11610 to 11800 kHz and everything outside that range is "down" in power. In fact it rolls off faster on the high side than it does in the 11175 kHz area.

T!
 

brandon

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It stopped about 15-20 min ago, just as if someone hit a switch. It was coming in pretty good at the time prior here in SoCal.

Sent from my SAMSUNG-SGH-I727 using Tapatalk 2
 
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