[Spooks] HF Jamming

Sat, 29 Jun 2002 09:56:28 -0600

Actually, I live in Colorado.  I've had several experiences with jammed
stations the last few days.  While his problem could be something close by
generating wideband signals, I've had several AM stations here in Colorado
Springs that have had other carriers over the top of them.'

Last evening about 5 pm my time (29 Jun) several of our ham vhf frequencies
were "jammed".  It wasn't a channel by channel jamming.  It was a wide-band,
across about 10 mhz in the 144.000 area.  Our packet radio frequencies and a
lot of voice channels.  Strangely, it didn't get up into the main
frequencies where we have repeaters (and many of them won't come up unless
there are CTCSS tones on the transmitter to bring them up in the first
place).

A couple of the hams wrote it off as "atmospheric noise".  I haven't yet.
Unfortunately my DFing gear is gone (destroyed in a car accident a few years
back) and I've not had time to build new stuff.  I did determine the
"signal" was coming from Pikes Peak.  However, that doesn't mean anything, a
lot of us use Pikes Peak as a giant reflector and from aiming my big beams
west I can talk vhf and uhf into Kansas sometimes.

So... right now, it might be more of a mystery than everyone thinks.  If it
happens again, I'll be out and about today, and try to uncover the source if
it is local.

Take care.

Rick, n0njy

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Martin H. Potter
Sent: Saturday, June 29, 2002 8:15 AM
To: [email protected]
Subject: Re: [Spooks] HF Jamming

Hi, Tom,

If the jamming only occurs on signals that are already there, and on
every signal that is there (below some frequency), then a "first guess"
as to the source could be cross-modulation of some sort.  I assume there
are no copper oxide joints in your own antenna system but wonder if
there might be corroded metal-to-metal contacts somewhere in your
neighborhood or near an MF transmitter in your area.

73,
... Martin    VE3OAT

"Thomas A. Adams" wrote:
>
> Not really too sure which list to send this to, so going with WUN and
> SPOOKS mail lists.
>
> On the (local) evening of 26 June 02, (aprox. 0400 - 0500 UTC
> of 27 June), I was doing some BCB DXing, and was rather astonished
> to hear AM broadcast staions being jammed...   ALL of them above
> 1000 KHz! Upon investigation, I discovered that nearly EVERY signal
> I could hear at this location up to aprox. 4500 KHz was also being
> subjected to jamming!
>
> The jamming was discreet signals; i.e., not a broadband signal. It
> was specifically targeted at any and all radio emissions, and did not
> appear in unused spectrum between signals.
>
> The jamming appears to have been SSB signals modulated with a
> sound that I can only describe as similar to the sound effects from a
> 1950's science fiction movie. The closest I can describe it is like the
> sound of a movie ray gun. The jamming signals would go on for about
> one minute, and then break for 5 - 10 seconds, as if the source was
> checking it's jamming effectiveness, or looking for new signals to hit
> before resuming.
>
> EVERYTHING got hit; WWV @ 2500 KHz was nailed, numerous RTTY
> stations, and (rather illogically) the 75 meter ham band! That was
> interesting; numerous ham stations changed frequency to avoid the noise,
> and were promptly followed by the jamming to the new frequencies. The
> signal also appeared on the 2182 KHz marine calling / distress frequency,
> and on any other signal in the range.
>
> On at least one other occasion I've heard this sort of jamming, but I've
> never before heard it extend as low as the AM broadcast band.
>
> Tho the local noise level was sort of high on the AM band, I used my loop,
> unreliable as it is on skywave signals, to take rough bearings on the
> jammers observed in the broadcast band. Propagation was showing an
> opening to the Carribean (I'd just logged an AM station on Antigua), and
> that's the area where the loop showed nulls on the jammer; i.e., to the
> southeast of my Wisconsin location.
>
> A friend of mine reports that he observed similar jamming on the 80 meter
> ham band on Monday evening, and more of it (tho much weaker) on the
> 160 meter ham band later in the evening.
>
> I'd appreciate hearing from anyone else who may have observed this stuff,
> and while I have my own opinions on sources I'd like to hear what others
> think
> about it.
>
> 73's,
>
> Tom, W9LBB
>
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