[Spooks] HF Jamming

[Martin H. Potter]

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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