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Re: [RFI] Receiver settings for hearing RFI?

To: <rfi@contesting.com>
Subject: Re: [RFI] Receiver settings for hearing RFI?
From: "Paul Christensen" <w9ac@arrl.net>
Date: Sun, 11 Mar 2012 11:32:10 -0400
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
> The good news is that I own an Elecraft K3....the bad news is that I
> haven't bought a P3 yet.  It sounds like a P3 is on my wish list and
> maybe later some type of portable SDR  if I want to get really obsessive
> about this :)

Once you have a panadapter, it's easy to become obsessive in trying to get a 
flat noise baseline without any switch-mode "bumps."   Maintaining a flat 
baseline on all bands can involve a lot of continuous work -- and not all of 
it is switch-mode related.  On the upper bands, repeating spurs from LAN 
cabling, routers, etc. requires a lot of initial attention.  The good news 
is that I don't normally hear this interference from the neighbors as I do 
with their switch-mode appliances.

The moment a bump shows up, I'm headed to the breaker panel to start the 
next investigation.  Before owning a panadapter, these noise sources 
existed, but in the case of a low-level broad noise bump of say 40 kHz wide, 
you can easily sweep the receiver and not really know there's a problem. 
The noise floor gradually rises and it's easy to miss.

Another alternative to this is to use a noise nulling device from MFJ, 
Timewave, or DX Engineering.  N4LQ and others have been very successful in 
eliminating noise sources by electrically steering a null from a sense 
antenna.  The degree of success largely depends on keeping the noise antenna 
focused on receiving only noise and not desired signals.  For example, a 
ground mounted short vertical whip located near or under a horizontal 

Paul, W9AC

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