[RFI] Re: Mail failure

Cortland Richmond Cortland Richmond" <cortland_richmond@qmgate.optilink.dsccc.com
24 Mar 1998 10:07:26 -0800

                      RE>Mail failure                              3/24/98

RE>rfi-digest V1 #42                         3/24/98

Ed, K0il, writes

>>...The 2 inch long ferrite clamp on "beads" sold by radio shack are about $3 or $4 each.  I used about 25 of them on the Stereo and 10 more on the leads from the computer to mouse and keyboard and monitor." <<

These ferrites are usually not very effective at low frequencies.  Just as  a rule of thumb, I'd count on 50 to 100 ohms at 100 MHz and near ZERO ohms at 10 MHz for one pass of wire through the  core.

Where this many were needed, it is likely the same result could have been obtained by top-quality shielded cables, adding grounding clips inside or at the computer, adding additional shield over the existing cables, or combinations of these measures.  25 ferrites is a LOT of money, especially at Radio Shack's retail price.

Cortland, KA5S

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