[Amps] Holes vs. screen for chassis ventilation?

[Jim W7RY]

I use hardware cloth. About 3/16" between the wires. Available in many 
sizes. Its usually galvanized. Available at most hardware and home centers.

In other words, window screen with large holes.  It's easy to bolt onto the 
cabinet in the four corners. And it's very tough and lets lots of air 
through.

73
Jim W7RY


--------------------------------------------------
From: "Dan Levin" <dan at andlev.com>
Sent: Tuesday, October 05, 2010 8:24 PM
To: <amps at contesting.com>
Subject: [Amps] Holes vs. screen for chassis ventilation?

> Am building an HF amp, and will need several large (~3" diameter)
> openings in the chassis for ventilation.  I would like the chassis to
> be as RF tight as is reasonably possible, so trying to figure out the
> best strategy for shielding the openings.
>
> The two obvious options are to use a pattern of (small, say 1/4")
> holes, or to cut a big hole and then cover it with (presumably)
> aluminum window screen mesh or similar.
>
> I've searched for answers, but all I found was some general stuff that
> suggested that smaller holes were better, and to keep holes under
> lambda/30 if possible.  My guess is that fine grid aluminum mesh (as
> in window mesh) would do better than holes - but since I am having
> Protocase build my chassis, patterns of small holes are actually
> easier for me to implement (since they can cut those, but I have to
> deal with the screen myself).
>
> Anyone have either a) answers or b) pointers to good sources?
>
> Thanks!
>
>                                     ***dan
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