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
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
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
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
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
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