[RFI] Computer RFI on 160

Jim Brown jim at audiosystemsgroup.com
Wed Oct 29 16:14:35 EDT 2008

On Wed, 29 Oct 2008 15:40:52 -0400, Bill Tippett wrote:

>On-site I tried about 8 turns of the
>power cord through a Mix 31 2.4" toroid, but that didn't dent the
>noise enough.  

I wouldn't expect it to. You need at least 14 turns on a single #
31, and more turns or more toroids in the stack is better. Use my 
measured data for RG8X on these cores as a starting point. In 
essence, you've got to move the low Q resonance of the ferrite 
choke down to 2 MHz. 8 turns on a single #31 puts the resonance in 
the 5-7 MHz range. 


It's good to hear that the Corcom filter worked for you. A surplus 
warehouse in the Bay Area has a bunch of filters like you 
describe, and they have an internet presence. I've seen Corcom, 
Delta, and several other brands there at good prices. 


There's also good data for Corcom and Delta on the internet. 
Google on part numbers to find it. 


Jim K9YC

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