I have a Grundig SW rig, but I find the HT (wideband receive w/ AM) with a
step attenuator and a small shielded loop to be more useful. Also have a
simple coax faraday pickup for in close.
The issue is that the signal is strong but *SHORT*, think snap your
fingers short, and while it may repeat after a few seconds the long term
average is a couple times a minute or less.
If I had a second or 2 to rotate the loop... But I don't.
I even tried connecting the loop to the main tranceiver mounted to the
desk so that I could try to plot long term averages while rotating the
loop 5 deg every 10 minutes. Only problem, the peak reading for the pulse
varies up to 40db from pulse to pulse.
I am pretty much down to guessing likely canadates, adding enough
attenuation to lose the pulses, and then placing the loop phyically close
to suspect devices and waiting. The only thing I do know is that it is
not in home or a reciever generated issue. All AC power cut, still there.
2 seperate HF rigs and an HT on three seperate antennas, still there on
all three.
Even went as far as listening on one receiver/antenna, then cutting power
to that receiver and powering up another just to totally rule out the
radio gear as a source.
I keep hoping that whatever the device is it is some form of
"statekeeping" status, and that I can catch it in an active state
generating pulse trains of 10 seconds or longer so I can properly DF it.
On Sun, 12 Jul 2009, Frank Haas KB4T wrote:
> I would use a handheld shortwave receiver (Grundig E5 or equivalent)
> and take a walk around the house and neighborhood when the
> interference is occurring with some regularity. The receiver would be
> tuned to the frequency at which the signal is strongest until I got
> close then I would either tune off the strongest frequency slightly
> and look further for an increase in signal strength or tune to a
> harmonic multiple of the strongest frequency to see if the strength is
> lower.
>
> The receiver should have some sort of signal strength indicator and an
> attenuator. The high end alternative would be something like the ICOM
> R-3 with a step attenuator attached via a barrel male BNC adapter and
> a small loop antenna to find nulls.
>
> I have tracked down HF interference sources using a small loop antenna
> I bought from Antennas & More (If I recall correctly) and an R3. By
> walking or driving in a circle (more or less) around the perimeter of
> the interference, I was able to find nulls and draw lines on a map.
> Where the lines crossed I went in close and found the source.
>
> Sometimes, if you are lucky, pulsing sources will be rich in harmonics
> so that when you get in close you can hear them at successively higher
> frequencies into the VHF spectrum. If I can hear the source in the VHF
> spectrum I can usually DF it with a smallish Yagi and a receiver with
> an attenuator.
>
> Good luck!
>
> 73,
>
> Frank N. Haas KB4T
>
> -----Original Message-----
>
> Message: 1
> Date: Sat, 11 Jul 2009 02:44:11 -0500 (CDT)
> From: "Christopher E. Brown" <cbrown@woods.net>
> Subject: [RFI] Looking for ideas about yet another noise source
>
> Attempting to track down a bothersome very intermittant noise and
> looking for some ideas. Don't have a decent way to record it, but may
> need to set something up if I cannot make headway.
>
> Noise is pulse, appears on at least 80-20, strength higher around 20.
>
> On the lower freqs, it is more of a static rush but time compressed,
> it is also seemingly random, twice in 5 seconds, nothing for 40 sec,
> once, and so on. Seems to be there almost any time of the day or
> night.
>
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>
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