From: karn@qualcomm.com (Phil Karn)
Date: Wed, 7 Apr 93 15:22:56 PDT
To: cypherpunks@toad.com
Subject: EMI shielding
Message-ID: <9304072222.AA29676@servo>
MIME-Version: 1.0
Content-Type: text/plain


Apropos the recent discussion about TEMPEST shielding, there's an
interesting product that might prove quite useful: CAPCON EMI
suppressant tubing. A colleague got a shipment of it today.

It's ordinary black rubber tubing that has been loaded with iron
oxide. It comes in 26 sizes from .04" ID to 1.25" ID, and is claimed
to have much better attenuation than ferrite beads, especially at UHF
and microwave frequencies.

You can shield entire cable lengths with it, or you can apply it in
short segments (1" to 1') just like ferrite beads and get plenty of
attenuation for less cost and weight (this stuff is *heavy*, and the
1/2" stuff cost several dollars per foot.)

It's also available as sheeting in various thicknesses for lining
cabinets, etc.

I got the bright idea to test the absorptivity claims for this stuff
by putting an 8" piece into a microwave oven. After 10 seconds, it was
too hot to handle. I'd say it's doing just what it's supposed to do.

Contact info:
Capcon, Inc
147 W 25th St
New York, NY 10001
212-243-6275
212-645-0185 (fax)

Phil