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Re: [RFI] High Noise Floor

To: "Roeder, Landon" <LRoeder@nespower.com>, <rfi@contesting.com>
Subject: Re: [RFI] High Noise Floor
From: "Tom Rauch" <w8ji@contesting.com>
Reply-to: Tom Rauch <w8ji@contesting.com>
Date: Mon, 8 Oct 2007 21:29:37 -0400
List-post: <mailto:rfi@contesting.com>
> We have a customer who contacted us regarding "RFI" at his 
> home station.
> We were able to trace a single source to an underground 
> water pump
> operated by Metro Water.  (What a weird noise that was.) 
> Even though
> that noise is clear, he is still complaining about what he 
> believes to
> be RFI on 75m with his SteppIR vertical .  Using our Radar 
> Engineers
> MODEL 240-A, we are able to see an elevated noise floor, 
> but there are
> absolutely no distinguishable power line signals.  The 
> "noise" is also
> audible/visible when mobile in his neighborhood.  Other 
> than the usual
> isolation techniques inside the home, how can we help him 
> determine the
> source of a signal that has no noticeable characteristics, 
> other than an
> elevated noise floor?  Realizing that this is no longer 
> the power
> company's responsibility, what recommendation would you 
> offer him?


What type of lines are in the area? Some lines can elevate 
the noise floor without sounding too much like power line 
noise if they are three phase with bad corona on all phases. 
Think of it as an arc that never extinguishes in all three 
phases at the same time.

I'm a little puzzled that you cannot find a change in noise 
level with distance as you drive around and pinpoint a 
source. How high in frequency do you hear the elevated 
noise? A friend of mine had a noise problem on 75 meters, 
well over S-9. The power company found nothing. I found the 
problem nearly two miles from his house. They fixed the 
lightning arrestor and his noise vanished.

Not saying you have a problem, you may not. But sometimes 
the noise can follow power lines a very long distance. He 
especially has a problem with a vertical. I hope he has an 
excellent ground on it, or else he has to have some good 
feedline decoupling.

73 Tom 

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