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Re: [TowerTalk] Halogen Bulbs - 1.8 Mhz RFI

To: "" <>
Subject: Re: [TowerTalk] Halogen Bulbs - 1.8 Mhz RFI
From: "Jim Brown" <>
Reply-to: Jim Brown <>
Date: Thu, 25 Nov 2004 14:16:01 -0600
List-post: <>
On Thu, 25 Nov 2004 14:46:07 -0500, Floyd Sense wrote:

>I doubt that there is much you can do to silence them.

I agree that there are probably switching supplies causing the problem, 
but I wouldn't give up on fixing the problem without trying.  

There are three basic ways the RF can get out -- on the power line 
wiring, on the low voltage wiring to the lamps, and direct radiation from 
the power supply if it is unshielded.  Direct radiation you probably can't 
fix except by replacing the supply. A standard, good power line filter 
should eliminate what is coming via the power line, and a multi-turn 
choke around a big ferrite, possibly in combination with a capacitive filter 
should be able to kill what is on the low voltage wiring.  

You will need at least 8 turns around the typical big toroids to make an 
effective choke for 1.8 MHz. That choke should also work on 80 meters, 
but may be running out of effectiveness by 40 meters and above. 


Jim Brown  K9YC


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