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Re: [RFI] Ferrite Beads

To: "Jim Smith" <jimsmith@shaw.ca>, <rfi@contesting.com>
Subject: Re: [RFI] Ferrite Beads
From: "Ford Peterson" <ford@cmgate.com>
Date: Wed, 20 Oct 2004 19:35:46 -0500
List-post: <mailto:rfi@contesting.com>
Jim wrote:

> The moral of the story is that you have to watch that air gap.  When you 
> split your toroids, if a bunch of the material crumbles away you will 
> have an air gap.

I use a machinist vice to do the dirty deed.  By separating two blocks to the 
approximate diameter of the toroids, and using a drill bit on the opposite side 
of the core, in the middle between the blocks, the vice will split them in two 
nearly perfect every time.  As long as you keep the halves matched up in pairs, 
they can be placed back together with an almost imperceptible crack between 
them.  I think the coupling in this manner is actually much better than the 
traditional split cores could ever be.

I'm getting lots of conflicting information regarding this stunt (some through 
this list and some direct).  Some feel that the cores with one turn through 
them will not create enough resistance to make much, if any, difference in the 
noise.  I still have not decided what to try next.  Buying 48 to 96 cores at 
$1.20 to $1.70 each, and snapping them in two, seems like a waste of money, 
energy, and otherwise perfectly good toroids if it is not going to work.  How 
much RF resistance would be required to make a noticable difference?  I'm not 
smart enough to know.  Perhaps others on this list could provide some guidance 
for me.  Is 20 ohms on each COP enough?  Is 50 ohms enough?  How about 300 
ohms?  I have no experience with this type of problem and therefore I'm truly 
clueless.

Ford-N0FP
ford@cmgate.com




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