[RFI] shielding question
George Johnson
w1zt at comcast.net
Mon Dec 22 17:10:23 EST 2003
Dave,
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 at arrl.net
>web: http://www.k1ttt.net
>AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
>
>
>
>
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