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Re: [RFI] Computer cases and RFI

To: rfi@contesting.com
Subject: Re: [RFI] Computer cases and RFI
From: "Martin, AA6E" <martin.ewing@gmail.com>
Date: Mon, 2 Jan 2006 17:36:24 -0500
List-post: <mailto:rfi@contesting.com>
This is a case (no pun intended) where it would be good to have some
data.  Obviously, an open hole has no shielding value, but the normal
computer case with a metal panel may not be a lot better.  At least
the one on my desk has no positive electrical connection with the main
case.  One screw and a couple of fingers for the mechanical

The good news is that this system is "quiet enough" for me, even with
the panel off.  When I have troubles, it's always with the external
cabling.  (Without chokes, external wiring can be an efficient
radiator - comparable in length to a wavelength.) A truly RF-tight
computer would look a lot different than the ones we normally see.

Of course, all bets are off when you put in the neon lighting to show
off your custom box.  You did buy the motherboard with the fluorescent
connectors, didn't you?

73 Martin AA6E

On 1/2/06, Alan NV8A <nv8a@att.net> wrote:
> In my local independent computer store today I saw a variety of cases
> for the build-it-yourself types (among which I include myself), but was
> surprised to see some totally transparent ones. I asked one of the store
> employees whether these had any shielding (e.g., in the form of a
> transparent metallic coating on the inside), and he said he was sure
> they did not and that he would not want to use one himself.
> So here is the question: computers are supposed to comply with FCC
> emission regulations, but how can a computer built into such a case
> pass? Granted that home-brew computers don't get tested, but can a store
> legally sell someone a custom-built computer (this store does: you
> choose your case and what components you want in it) that could never in
> a million years pass the FCC tests?
> I wonder how many such RF-pollution generators are in use.
> Alan NV8A
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