[RFI] RFI Direction Finding

Jim P jvpoll at dallas.net
Sat Feb 18 00:03:22 EST 2006

----- Original Message ----- 
From: "Ed -K0iL" <eedwards at tconl.com>
To: "'Paul Christensen'" <w9ac at arrl.net>; <rfi at contesting.com>
Sent: Friday, February 17, 2006 8:18 PM
Subject: Re: [RFI] RFI Direction Finding

> The fact that you cannot rcv it at VHF indicates the source is some
> away from your station.  It's either being conducted via lines to your

This assumes that the source is flat from HF through VHF. This isn't
always the case.

> vicinity or it's just far enough away to be out-of-range on VHF but not on
> HF.

The WORST source ever in my area affected another ham a mile
north or so of me who went out DRIVING with an all-mode 2M rig
and a beam didn't find the source.

I did. I found it with my ferrite loopstick Sears Model 2278 4-band
AM/FM/SW1/SW2 battery powered portable radio.

The first 'radial' (null - pointing to the source) was obtained
by standing out in front of the house in the street and nulling the
source. Of course, I didn't know which of the two headings
(180 degree ambiguity using nulls of course) I had obtained
the source would be one, so I picked one and that was it.

This WORST HF noise source ever didn't make much of a fuss
on the FM Broadcast band either when close; no wonder the
other ham didn't find it in the 2M VHF spectrum.

> Track it on the highest freq at which you can rcv it moving to higher
> 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
> stronger peaking.

Very good advice.

I love those sources that radiate into 450 MHz area where I
can use a 7-element Yagi and DF right to the house or
pole. Those are kinda rare though, although shorted
doorbell transformers and arcing 'dust' filters are easy
to DF this way.

Jim P  -- WB5WPA --

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