Hi,
>From what I have seen, it is a power line transport issue most of the
time... While the power company is not to blame, the power lines are
none the less involved in the transport. Most RFI I have seen is not
specular in nature. The RFI phase shift boxes work best on a point
source, which is not most RFI. Don'
t get me wring, they can help, but it is just that, a small help, not a
full removal of RFI.
You have an RFI source, say a lighting system, which is feeding the
house wiring, which in turn is feeding the power grid itself. See
Loftness's book for details on how if you are interested.
The most recent locate I had was a house well over one thousand feet
from my home, it was dead quiet in front of the house, at the street
with the house wiring being direct line of sight to the receiver. The
give away was the RFI coming from the grate in the ground in front of
the house... It was covering a vault which contained the transformer
feeding that home.
I had a 30 over S9 RFI source, on 40 and 30 meters, well over a thousand
feet away from that location. The RFI was being generated by a set of
grow lights, the RFI was being conducted from the source house via
underground power grid wiring, across a street, (underground, and thus
not hearable), to a riser on a pole, above ground, where it became
hearable again.
Once on the power grid, the RFI ran everywhere. As far as I can tell,
the riser was acting like a vertical antenna, which gave this RFI one
hell of a vertical punch, much more than expected, while the horizontal
power grid wires just scattered it everywhere.
The result was an un-nullable RFI signal with one of the little boxes
MFJ, or Timewave sells. The RFI was not specular in nature so the
arrival times were scattered everywhere, no single event arrival time to
work on, so nulling it was not possible.
Up to now, myself and several other hams have located five RFI sources
in the area, all of which were being transported via the power grid,
across distances as far as a mile or more.
In one event, there was a ham close enough to get direct radiation from
the house, so in short, yes it is a power line issue most of the time
causing the RFI, and no the Null boxes don't work all that well on that
sort of RFI. If you have a sparking lightening arrester, then you can
get some help with a box like that, but if the power grid is scattering
it, you lose...
--
Thanks and 73's,
Dave (NK7Z),
Moderator Yahoo's MixW group, Yahoo's Dopplergram group, and Yahoo
MM-SSTV group.
For equipment reviews see: http://www.nk7z.net
On Sun, 2013-09-29 at 20:30 -0600, Tom Thompson wrote:
> It's generally not on the power lines. It's on the house wiring and is
> a point source at the house.
>
> On 9/29/2013 7:51 PM, David Cole wrote:
> > They don't work so well on RFI distributed by Power Lines... The source
> > is not point in nature.
>
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