[RFI] Ferrite Beads

Tom Rauch w8ji at contesting.com
Wed Oct 20 22:42:08 EDT 2004

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.>>

No one could possibly answer that unless they worked on the
same vehicle.

The amount of impedance you need depends on the common mode
impedance of the system you are working on and it could be
anything. The lower the common mode impedance, the larger
effect a low impedance bead will have.

This is why a combination of bypassing, grounding, and beads
is far more effective than beads alone.

73 Tom

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