> Then I had to go to 450 MHz to get a bead on
> the specific pole and hardware.
I would underscore the *very* good results I've
seen using a dipole cut for TV CH 3 (and
mounted to a 4' length of PVC pipe) used in
conjunction with a TV field strength meter;
in fact, I can get nulls of the ends of that
dipole that puts put the DFing of the same
'source' using a UHF hand-held beam to
shame!
Some sources, it turns out (as evidenced by
actual 'field work') aren't always as strong
(or even the the same one) when the frequency
bands are as disparate as HF and UHF (14 MHz
and 450 MHz say). Just a note of caution
when actually looking at this stuff in the field ...
When tracking down such sources as switching
power supplies, *nothing* beats a receiver that
is capable of tuning the same range _that you
are being affected on_ (primarily HF). For this a
self-contained receiver with a _ferrite loopstick
receiving antenna_ has been the 'bees knees'
for me. I continue to 'log successful kills' using
this receiver to this day. When doing some DFing
with a receiver like tis, _ it is important to get out
and walk the streets_ , do a little leg work coupled
with copious mental notes of where the signal is
STRONGEST and what POINT all bearings seem
to indicate.
I would also, once again, emphasize the importance
of being able to detect, or measure the *peak*
of some of these low duty cycle, high peak power
power-line noise sources, as opposed to the highly
averaged readings/responses of a simple AM
detector that most scanners capable of AM use.
That's not to say that some of these 'lesser'
means receiving are not valuable, given the
alternative of nothing at all!
Jim P / WB5WPA /
----- Original Message -----
From: "Cortland Richmond" <ka5s@earthlink.net>
To: <rfi@contesting.com>
Sent: Sunday, March 20, 2005 10:58 AM
Subject: [RFI] Direct DFing of arcing hardware (was PG&E IR line
faultdetection advertisements)
>
> Some 20 years ago I had occassion to track down widespread interference
> caused by medium-voltage power-line-related arcing. I found HF DF of
> limited use due to RF conducted along powerlines and other conductors to
> be radiated elswhere. I had to go into VHF to narrow down the general
area.
> Then I had to go to 450 MHz to get a bead on the specific pole and
> hardware. The hardware involved was almost resonant there, so the *direct*
> emission could be DF'd.. Luckily, it turned out to be at a local airport
> and had been bothering the control tower's reception for some time; when
> THEY complained, the utility showed right up.
>
> This calls for beams, not loops, of course, and I had to build one.
> Nowadays I have 2450, 1700, 1250, 900 MHz, and 2/440 as needed.
>
> Cortland
> KA5S
>
>
>
> > [Original Message]
> > From: Kevin J. Rowett <krowett@rowett.org>
> >
> > Almost all the source of HF RFI is sparking noise caused by current
> > "arcing" over between one of the conductors and ground. This
> > usually only happens with the medium (15-48kV) voltage distribution
> > lines and the even high voltage lines (> 55kV).
>
>
>
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> RFI@contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>
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