[Beowulf] Re: Not all cases need be metal

[Alan Ward]

You are right, of course. This also explains why all laptops have metal lining behind their funky (or not) plastic cases.

In my experience of running with cases open, no case at all, or even using a cardboard boot box as a case (yep, a student brought that in once :D) , the worst interference is with loudspeakers. Nothing much is detected with TV sets, radios or cell phones. I guess it's just that loudspeaker wires are so much longer than other equipment.

On the other hand, metal cases that are not appropriately isolated from the inboard electronics may act as emitting antennae, actually increasing interference with other equipment. Seen that mainly with some low-end tower boxes.

Cheers,
-Alan



-----Original Message-----
From: beowulf-bounces at beowulf.org on behalf of David Mathog
Sent: Tue 10/28/2008 12:32 AM
To: beowulf at beowulf.org
Subject: [Beowulf] Re: Not all cases need be metal
 
I missed most of this thread, so somebody may have already pointed this
out, but cases are metal not just for fire safety reasons.  The case is
usually made of a good conductor so that it will also shield the radio
emissions from the electronics housed inside.  Failure to do so could in
theory bring the wrath of the FCC down on you (in the U.S.), or at least
make you really unpopular with your neighbors.  I wonder if the new
digital TV tuners are more or less sensitive to this sort of thing than
were the old analog tuners?  I'm thinking they are likely to be more
sensitive, since weak channels we could pick up with varying amounts
of "snow" and multipath using an analog tuner tend to be a big nothing
with a digital tuner.

David Mathog
mathog at caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech
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