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Re: [RFI] shielding question

To: "Jim Brown" <jimbrown.enteract@rcn.com>,"RFI List" <rfi@contesting.com>
Subject: Re: [RFI] shielding question
From: "Tom Rauch" <w8ji@contesting.com>
Reply-to: Tom Rauch <w8ji@contesting.com>
Date: Mon, 22 Dec 2003 19:51:41 -0500
List-post: <mailto:rfi@contesting.com>
Hi Jim,

> I can do both. It's called "shield-current-induced noise," (SCIN). It
> was first described by Neil Muncy (ex-W3WJE) in an AES paper in 1994,
> based on research he did only at audio frequencies. I've done more
> research on it in the last year or so, publishing my research in two
> AES papers -- one in March, 2003, presented in Amsterdam, and one in
> October, 2003, presented in NYC. Neil's 1994 paper and my March paper
> are available from the AES (www.aes.org). The October paper will be
> there in a few months (for some reason, it takes a while after the
> convention to get it there). My March paper extended Neil Muncy's work
> to 4 MHz, the NY paper took it up to 300 MHz. Both of my papers include
> lots of data on real cables, and show the effect of various cable types
> on RF detection in equipment. They also document my test setup, and
> report of field testing of cables and equipment when exposing it to ham
> transmitters on Field Day, and to broadcast transmitters.

I'm fascinated by the RF part of this, since the RF part runs contrary to
what I have measured.

No question the drain COULD carry considerable common mode current at low
frequencies, but it strikes me very odd it could at frequencies where the
foil is more than several skin depths thick. Even if the drain would
slightly perturb balance, I don't see how this would apply in a case like
this where skin depth isolates everything inside the cable from the outside.

Especially to the extent that the shield would be noticeably degraded,
making the shielding worthless or ill-advised.

That's a big site. How would one go about finding the paper on that site?
Maybe there is something I'm missing.

73 Tom

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