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Re: [RFI] RFI Direction Finding

To: "'Paul Christensen'" <w9ac@arrl.net>, <rfi@contesting.com>
Subject: Re: [RFI] RFI Direction Finding
From: "Ed -K0iL" <eedwards@tconl.com>
Date: Fri, 17 Feb 2006 20:18:52 -0600
List-post: <mailto:rfi@contesting.com>
The fact that you cannot rcv it at VHF indicates the source is some distance
away from your station.  It's either being conducted via lines to your
vicinity or it's just far enough away to be out-of-range on VHF but not on

Track it on the highest freq at which you can rcv it moving to higher freqs
the stronger it gets.  You'll notice standing wave peaks and nulls as you
approach the source--ignore those peaks looking for an overall stronger and
stronger peaking.

You could use your AM radio in the car to track to the approximate vacinity,
then switch to an AM-VHF radio to find the correct pole or group of poles.
If the AM radio doesn't work, I've also seen loop antennas used for HF
tracking using the null in the pattern.  You could probably find some plans
by searching for "HF Loop Antennas" on google.

73, de ed -K0iL

-----Original Message-----
From: rfi-bounces@contesting.com [mailto:rfi-bounces@contesting.com] On
Behalf Of Paul Christensen
Sent: Friday, February 17, 2006 2:40 PM
To: rfi@contesting.com
Subject: [RFI] RFI Direction Finding

I am looking for a handheld DF unit capable of reasonable directivity on
40M.  I have excessive (+10 dB/S9)  power line noise centered near 7 MHz but
the noise is not very detectable at VHF/UHF.  I realize the gain will be low
for a handheld unit, but is there a device I can use to establish good
directivity at 7 MHz within a reasonable size for walking or mobile mounted?

-Paul W9AC

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