Re: [SI-LIST] : Chassis hole opening and frequencies

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From: Istvan NOVAK (istvan.novak@worldnet.att.net)
Date: Thu Dec 30 1999 - 16:42:56 PST


Doug,

Since the SI-list seems to be quiet in these days, let me give you some
quick answer until EMC gurus jump in. Electromagnetic wave can go through
openings with little attenuation as long as the longest dimension is larger
than half the wavelength. This defines a cutoff frequency below which wave
propagation is not supported, and the wave is attenuated exponentially with
distance (along the thickness of the wall that has the opening).

A good start for further references is e.g., the Don White's "EMC
Encyclopedia". You may also want to ask around and/or join the emc list:
Here is the footnote from one of the messages:

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I hope this helps

Istvan Novak
SUN Microsystems

----- Original Message -----
From: Doug Brooks <doug@eskimo.com>
To: <si-list@silab.eng.sun.com>
Sent: Thursday, December 30, 1999 12:45 PM
Subject: [SI-LIST] : Chassis hole opening and frequencies

> As I recall, there is a relationship between a hole in a chassis and the
> frequencies that can pass through that opening. I recall that the longest
> dimension of the hole defines the wavelength, or quarter wavelength, or
> something, of the lowest frequency than can conveniently enter or escape
> through the opening.
>
> Can anyone give me the correct relationship?
>
> Thanks.
>
> And Happy New Year to All...........
>
> Doug Brooks
> and all of us here at UltraCAD
>
>
>
>
>
> .
> ************************************************************
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> Doug Brooks, President doug@eskimo.com
> UltraCAD Design, Inc. http://www.ultracad.com
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