Those Doppler shift antennas won't work on noise. They require a carrier,
preferably unmodulated, to detect the Doppler shift on while they rotate the
array.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: Roger (K8RI) [mailto:k8ri@rogerhalstead.com]
> Sent: Monday, July 13, 2009 00:47
> To: kb4t@arrl.net
> Cc: rfi@contesting.com
> Subject: Re: [RFI] Looking for ideas about yet another noise source
>
>
>
> Frank Haas KB4T wrote:
> > Chris:
> >
> > The random nature of your pulsing interference means you will have to
> > invest more time to find the source. It's not going to be easy and
> > will likely be very time consuming because of its intermittent nature.
> > You have the right tools so now you have to use them to the best
> > advantage.
> >
> How about building up one of those "doppler shift" antennas? I've seen
> them used on 2-meters and for close in work I'd think it could be
> adapted to 20.
>
> For years I've chased what at times can be an obnoxious and loud hash.
> It should be easy to catch as it's often on for some time, but
> unfortunately when I get the chance to chase it, every time I get about
> a city block to the SE it disappears and does not come back. It's like
> they are watching for me...Nothing like a little paranoia.
> When it's on it's loud at well over S-9 including the entire 6-meter
> band, down to some where a bit above 40 meters. It's normally a day
> time signal that is strong from the NE to S where it fades rapidly. The
> only electric fence in that direction is probably a bit over a mile.
> While there is one to the S that I've never heard. There is one of the
> big high tensions lines that at its closest is about a quarter mile to
> the NE but I've never heard anything in that direction.
>
> OTOH I haven't heard it in over a year.
>
> 73
>
> Roger (K8RI)
> > Keep a log and note the day(s) and time(s) that the interference
> > occurs. Is there a time/day when it seems to occur more frequent. If
> > you keep a log for several days, do you note an increase or decrease
> > in activity.
> >
> > Is the activity level affected by environment? Day or night, warm or
> > cool? Prime time vs. Daytime? Trend analysis may show you better times
> > to hunt the source.
> >
> > If you are convinced that the source is not in your home, you will
> > have to start walking around the neighborhood particularly at times
> > your trend analysis says you are likely to hear the source.
> >
> > If the signal level varies from moment to moment you will have to note
> > the highest and lowest levels and try to find an attenuator setting
> > that gives you something in the middle. Another approach might be to
> > set the attenuator so the level is more or less consistently low and
> > start moving around to see if there are any locations where the signal
> > strength seems higher?
> >
> > I could go on and on but hopefully by now you see my point. Thorny
> > problems like yours require collecting more data and thinking more
> > about how you can use your tools to your advantage. Invest the time
> > and use your tools wisely and you will locate your source.
> >
> > I can't encourage you enough NOT to SPECULATE as to what the source
> > might be. In my experience, guessing what the source might be has been
> > a waste of time. Even with all the experience I have now, I rely on my
> > tools to lead me directly to the source. The only meandering I'll do
> > is in the early stages of the hunt when I'm trying to find the general
> > direction I must take to the source. Once I get a "lock" I focus on
> > that direction. Sometimes it takes a bit of effort to get the "lock"
> > but that's what the trend analysis and wide open receivers do for me.
> > I prefer to work smart rather than work hard. I hate to waste time so
> > I limit guessing as much as possible.
> >
> > Good luck & 73,
> >
> > Frank N. Haas KB4T
> >
> > -----Original Message-----
> > Message: 4
> > Date: Sun, 12 Jul 2009 02:33:05 -0500 (CDT)
> > From: "Christopher E. Brown" <cbrown@woods.net>
> > Subject: Re: [RFI] Looking for ideas about yet another noise source
> > To: kb4t@arrl.net
> > Cc: rfi@contesting.com
> > Message-ID: <Pine.LNX.4.64.0907120217560.19313@tree.woods.net>
> > Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
> >
> > 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.
> >
> > _______________________________________________
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> > RFI@contesting.com
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> >
> >
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