It looks like harmonics from a Switch Mode Power Supply (SMPS)and since
almost all electronics use SMPS technology it could be anything from a
TV to a computer to a battery charger. Good job on eliminating your QTH
as the culprit and you are on the right path for finding it in the
neighborhood. Not sure how close your homes are in your neighborhood
but smart money says to start with the houses closest to your antennas
and work farther out. A receiver with a loopstick antenna should give
good directionality and be able to isolate a QTH as a potential source
before you ask everyone in the neighborhood to pull their breakers.
Earl N8SS
----------------------------------------------------------------------
Message: 1
Date: Wed, 19 Nov 2008 14:53:52 -0500
From: "Paul Christensen" <w9ac@arrl.net>
Subject: [RFI] Line Noise Spectragraph
To: <rfi@contesting.com>
Message-ID: <005401c94a80$8cbb8a60$063ca8c0@Dorm>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
Once again, I am at my wits-end. Just when I got the utility company to
clean up a four-year noise issue, I now have this. Please see the
linked
spectrograph below.
http://216.229.20.37/images/W9AC-Line-Noise.JPG
Beginning down around the BCB, I have the following noise pattern every
~ 56
kHz. The linked photo is centered on 3601 kHz but it extends well above
and
below that. Span of the graph is 190 kHz.
The frequencies of this noise pattern do not change. Tomorrow or a
week
from now, the pattern will look the same and the frequencies will be the
same -- so I would rule out a random power company arc of some sort
where
the frequency and broadness changes.
In AM mode, I hear what sounds very much like an SCR buzz with no
apparent
sign of modulation. It's always there (i.e., not something a neighbor
is
turning on/off) Does this look like an electric fence? Plasma TV, fish
tank aerator?
It is not coming from my home. I pulled the main 200A breaker and fed
my
transceiver by battery power. All home alarm battery systems were
completely shut down and removed from their power source.
I will soon use a small SWBC receiver to try and hunt for this but after
four years of dealing with the other noise issue, I'm getting sick and
tired
of feeling guilty when the neighbors want to know why I'm running all
over
the place in our gated community.
Any help as to the pattern would be greatly appreciated and I mean
greatly.
Paul, W9AC
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