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RE: [RFI] Power Line Noise in Indonesia

To: "rfi@contesting.com" <rfi@contesting.com>
Subject: RE: [RFI] Power Line Noise in Indonesia
From: "Jim Brown" <jim@audiosystemsgroup.com>
Reply-to: Jim Brown <jim@audiosystemsgroup.com>
Date: Mon, 19 Jul 2004 08:39:24 -0500
List-post: <mailto:rfi@contesting.com>
On Mon, 19 Jul 2004 12:43:08 -0000, David Robbins K1TTT wrote:

>Since you say that the noise is better when it rains there are two
>possible explanations.  First, the insulator surfaces are cracked or
>have arc damage, in this case the rain is filling the gaps and causing 
>steady current instead of arcing.  These should be replaced.  The 
>is that the insulators are dirty.  In this case the arcing is between
>gaps in the contamination, when it rains the gaps are bridged or the
>contamination is washed off for a while, once the surface dries the
>noise starts again.  Power washing can remove contamination 
>shutting off the line, but must be repeated regularly if you are in a
>marine or heavy industrial area that contaminates them quickly.  I 
>also seen some surface treatments that can help prevent surface
>contamination, but not sure how widely these are available.

While we're on this general topic  -- one of my pro audio engineering 
friends has pointed out corona discharge as a chronic problem in 
coastal areas. Can someone address the mechanics of this problem 
and arcing at insulators in general?

I am of the opinion that it is the vertical downlead (running down the 
pole to earth) from protection devices that does most of the radiating 
of noise that is coupled from protection devices to this "ground" lead.  
Based on the height of a typical pole, this downlead is going to be a 
most efficient as an antenna between roughly 5 MHz and 10 MHz. 

Thoughts anyone?

Jim Brown  K9YC

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