Re: [DMCForum] Re: Lo-jack

["Andrei Cular" <andreic@xxxxxxxxxxxxxxxxxx>]

I don't remember all the details, but a faraday cage needs to have the
proper size mesh to block a frequency.  Just cause a data cable labeled
shielded doesn't mean it is good for all frequencies. Our DC Servo's have
different shielding than the AC servo's or a standard PC data cable.


Andrei



----- Original Message ----- 
From: "Jim Strickland" <ihaveanaccount@xxxxxxxx>
To: <DMCForum@xxxxxxxxxxxxxxx>
Sent: Thursday, January 22, 2004 6:23 PM
Subject: Re: [DMCForum] Re: Lo-jack


The only thing that I am convinced of is that a "metal shipping
container" does not seal very well.  By definition, no electromagnetic
signals can get inside a "faraday cage", which I thought a metal shipping
container would be very similar to.

If the shipping container or elevator was a metal box without openings,
it would get no signal inside.

Andrei is "onto something" about frequency, but only that significantly
increased frequency has a higher propensity for going through
non-metallic matter, and not being absorbed/reflected by it.

There are other methods we're aware of, such as ULF and ELF for
transmitting underwater, but i think that's irrelavent here.


Jim

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