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Re: [RFI] Common mode chokes

Subject: Re: [RFI] Common mode chokes
From: Larry Benko <xxw0qe@comcast.net>
Date: Fri, 19 Mar 2010 00:31:43 -0600
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
Jim,

I beg to differ with you.  Effective common mode choking is about 
impedance and not just resistance.  I know that if the impedance is 
nearly all due to inductance, external capacitances can render the choke 
less effective but there are plenty of common mode chokes made for 
narrow band usage that are parallel resonant.  You can hardly design a 
ferrite choke with enough turn to be effective at the low end of the HF 
range that does not go through the parallel resonant frequency within 
the HF range.

Larry, W0QE 

Jim Brown wrote:
> Larry,
>
> You're missing the point of how ferrite chokes work. IT'S NOT ABOUT 
> INDUCTANCE, IT'S RESISTANCE! An effective ferrite choke is a VERY low Q 
> parallel resonant circuit tuned to the frequency you want to suppress.  
>
>   
>
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