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Re: [RFI] RFI Proof Computer speakers needed!!!

To: "rfi@contesting.com" <rfi@contesting.com>
Subject: Re: [RFI] RFI Proof Computer speakers needed!!!
From: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Tue, 31 Oct 2006 23:03:17 -0700
List-post: <mailto:rfi@contesting.com>
On Tue, 31 Oct 2006 23:17:51 -0600, Tim Duffy K3LR wrote:

>Do you have any ideas?

Hi Tim,

Study the Ferrites and RFI tutorial on my website, especially the 
Power Point that includes material about "the pin 1 problem." The 
latter is a major cause of RFI, and virtually ALL computer audio 
gear (and nearly all ham gear) is built with pin 1 problems. In 
general, "computer speakers" are pretty close to the bottom of the 
barrel. They will have pin 1 problems, and they will likely be 
completely unshielded. In fact, nearly all powered professional 
speakers are also unshielded -- I can light them up with a 5W VHF 
talkie at 5 ft. 

Also see the discussion in the Ferrite tutorial about what I call 
"threshold effect." 

There are several other RFI papers there that should be helpful. 


I'd bet that >90% of the problem is input/output wiring acting as 
antennas and pin 1 problems letting it in the door. 


Jim Brown K9YC

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