On Tue, 31 Oct 2006 23:17:51 -0600, Tim Duffy K3LR wrote:
>Do you have any ideas?
Hi Tim,
Study the Ferrites and RFI tutorial on my website, especially the
Power Point that includes material about "the pin 1 problem." The
latter is a major cause of RFI, and virtually ALL computer audio
gear (and nearly all ham gear) is built with pin 1 problems. In
general, "computer speakers" are pretty close to the bottom of the
barrel. They will have pin 1 problems, and they will likely be
completely unshielded. In fact, nearly all powered professional
speakers are also unshielded -- I can light them up with a 5W VHF
talkie at 5 ft.
Also see the discussion in the Ferrite tutorial about what I call
"threshold effect."
There are several other RFI papers there that should be helpful.
http://audiosystemsgroup.com/publish
I'd bet that >90% of the problem is input/output wiring acting as
antennas and pin 1 problems letting it in the door.
73,
Jim Brown K9YC
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