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Re: [TenTec] RFI question for Orion and other TT rigs

To: tentec@contesting.com
Subject: Re: [TenTec] RFI question for Orion and other TT rigs
From: "James Duffer" <dufferjames@hotmail.com>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Wed, 29 Jun 2005 20:23:32 -0500
List-post: <mailto:tentec@contesting.com>
Thanks for the info.  I guess the shielding using ferrous (hi mu) was for 
low frequencies.

73, Jim  wd4air

>From: Sinisa Hristov <shristov@ptt.yu>
>Reply-To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
>To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
>Subject: Re: [TenTec] RFI question for Orion and other TT rigs
>Date: Tue, 28 Jun 2005 22:55:56 -0400
>James Duffer wrote:
> > I am not sure about the effectiveness of aluminium in shielding 
> > fields.  It seems that a high mu metal is the way to go for magnetic
> > shielding.  That is what they used on CRTs to prevent magnetic 
>At 60 Hz or audio frequencies aluminium is not effective
>in shielding against magnetic fields.
>However, at radio frequencies it works very well, provided
>that the circuit to be protected is completely enclosed and
>the shield thickness is large compared to the skin depth.
>For example, Agilent's E8358A network analyzer (300 kHz - 9 GHz)
>uses aluminium shielding exclusively and has no problem in
>achieving ~140 dB dynamic range. Orion uses ~1.8 mm aluminium sheets,
>which is almost 30 times the skin depth at 1.8 MHz. That can
>provide ~250 dB attenuation of the magnetic field.
>Sinisa  YT1NT, VE3EA

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