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

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From: Adrian Shiner (adrian.shiner@virgin.net)
Date: Thu Dec 30 1999 - 13:31:09 PST


Hello Doug,
Nice to see that we are discussing RF techniques as opposed to playing with
circuit simulators for a change.

A thin slot is a half wave antenna and can be related to a 1/2 wave dipole
of the same dimensions. The electric vector is at right angles to the
longest dimension of the slot. A slot with a cavity behind it (like an
equipment enclosure!) can be a very directional radiator (see Fig 5.3 of the
book referenced below)

A very good book on VHF and UHF antennas (Chapter 5 for slot antennas) is
"VHF and UHF Antennas" by R. A. Burberry. Published by Peter Peregrinus Ltd
on behalf of the (UK) Insititution of Electrical Engineers, ISBN Number 0
86341 269 6. If you can't get hold of a copy then I can get one for you (in
exchange for money of course!).

In short, in my experience, slots are bad news for SI or EM Compatibility
(choose which ever term suits your physical location). Any signal or power
path into or out of an enclosure needs careful design.

A happy & succesful new year to all

Adrian

----- Original Message -----
From: Doug Brooks <doug@eskimo.com>
To: <si-list@silab.eng.sun.com>
Sent: 30 December 1999 17:45
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
>
>
>
>
>
> .
> ************************************************************
> See our updated message re in-house seminars on our web page
> .
> Doug Brooks, President doug@eskimo.com
> UltraCAD Design, Inc. http://www.ultracad.com
>
>
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