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Re: [RFI] shielding question

To: "David Robbins K1TTT" <k1ttt@arrl.net>,"Rfi" <rfi@contesting.com>
Subject: Re: [RFI] shielding question
From: George Johnson <w1zt@comcast.net>
Date: Mon, 22 Dec 2003 17:10:23 -0500
List-post: <mailto:rfi@contesting.com>
With the shielded cable I would be tempted to just wrap the speaker conductors themselves on the ferrite (bifilar wound) to add common mode rejection to those lines and still ground the shield at the receiver end. The shield can stay open at the speaker end. You are trying to get rid of the common mode pickup and you have the benefit of both the shield and the ferrite to keep it out of the amp output/feedback circuit.

I had a similar problem with 30 ft unshielded "surround sound" speakers and did not have the luxury of shielded speaker leads. But the common mode choke plus an L-C filter on the receiver output took all of it out. I created the ground connection for the L-C filter because the receiver had no ground reference (two prong plug) at all.

Good luck and let us know how you make out,
George .. W1ZT

At 03:38 PM 12/22/2003, David Robbins K1TTT wrote:
This is probably more of a tvi reflector question... is there one of
those, or is this place good enough???

I get into my new dvd 5.1 speaker system.  I picked up some shielded
speaker wire and ferrites.  But what is the 'correct' way to implement
them?  Obviously at the speaker end of the wires there is no place to
ground the shield so that will have to float.  Or is there something
else I should do with it??  At the receiver end I can tie all the
shields together and to the ground there.  What about the ferrites?
Would you put one at the speaker end?  Just with the 2 speaker wires
through it or with the shield also??  And on the receiver end, put the
ferrites on just the 2 speaker wires between where the shields are tied
to ground and the receiver, or before tying the shields together??

David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net

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