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
>"magnetic"
> > 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
>interference.
>
>
>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.
>
>
>73,
>
>Sinisa YT1NT, VE3EA
>_______________________________________________
>
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