I've never seen the circuitry, but how did the old ADF equipment work?
Might it be adaptable with a computer and display to display and overlay
on a GPS moving map?
> 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
> David Robbins K1TTT
> e-mail: mailto:firstname.lastname@example.org
> web: http://www.k1ttt.net
> AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
>> -----Original Message-----
>> From: Roger (K8RI) [mailto:email@example.com]
>> Sent: Monday, July 13, 2009 00:47
>> To: firstname.lastname@example.org
>> Cc: email@example.com
>> Subject: Re: [RFI] Looking for ideas about yet another noise source
>> Frank Haas KB4T wrote:
>>> 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
>> 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.
>> 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" <firstname.lastname@example.org>
>>> Subject: Re: [RFI] Looking for ideas about yet another noise source
>>> To: email@example.com
>>> Cc: firstname.lastname@example.org
>>> Message-ID: <Pine.LNX.email@example.com>
>>> 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
>>> RFI mailing list
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