Problem finally solved after a couple months of working with what had been a
less than compliant neighbor (See photo of the noise source in the link from
my prior message below). After trying unsuccessfully to work with the
renter of the property, the property owner and I agreed to use the services
of an unbiased, third-party electrician to isolate the noise source while I
monitored the interference outside his house.
It turned out to be a small refrigerator hidden under the bed of his renter
(to keep the beer cans cold). Seems that the fridge is a Chinese import and
uses a switch-mode power supply (SMPS).
To isolate the noise source to the property, I used a Palomar LA-1 amplifier
with loop antenna. The strongest noise was in the 3-6 MHz area and the
Palomar 1.7 MHz - 6.0 MHz plug-in loop worked perfectly. In fact, the
nulling capability of the loop worked so well that I was able to tell the
property owner that I had localized the noise source to a near-exact part of
the house from the street some 150-200 feet away.
My understanding is that Palomar no longer produces the LA-1 amp, although
some of the coil sets can be purchased by some suppliers on the surplus
market. Too bad. That's an awesome antenna for triangulating SMPS noise.
I had actually located the noise back in November. It has taken me since
then just to negotiate with the property owner. Although the renter is
responsible for the generation of the noise source from their personal
property, the reality is that you may end up having to work with the
property owner to reconcile a leasehold noise issue.
Despite the weight and size utility of switch-mode power supplies, I truly
wish the device had never been invented in the first place.
Paul, W9AC
----- Original Message -----
From: "Paul Christensen" <w9ac@arrl.net>
To: <rfi@contesting.com>
Sent: Wednesday, November 19, 2008 2:53 PM
Subject: Line Noise Spectragraph
> 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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