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[RFI] rfi to computer via sound card

To: <rfi@contesting.com>
Subject: [RFI] rfi to computer via sound card
From: n4zr@contesting.com (Pete Smith)
Date: Thu, 30 May 2002 16:39:47 -0400
I'm setting up to record contests using an SB-16 sound card and Recall Pro 
software.  At the moment I'm dealing with a severe RFI problem, which 
crashes the Recall software a few seconds into every transmission.  I've 
determined that it is definitely coming in the [line in] cable from my 
radio's external AF output, because when I disconnect that line from the 
computer the program doesn't crash no matter how long I transmit.  I've 
grounded the computer case and wound a number of turns of the [line in] 
cable around ferrite toroid cores, all without apparent benefit.  Would it 
make sense to try .01 disc caps bypassing the conductors in the [line in] 
cable to the shield, in case this is differential mode interference rather 
than common mode, as I'd assumed?

73, Pete N4ZR

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