[DMCForum] Re: Lo-jack
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[DMCForum] Re: Lo-jack



We have faraday cages at the State Dept. We call them "scif's" They
are much more than just a metal box.

They are also not steel. They are copper. In between sheets of copper
is a copper or steel mesh. The doors have mesh as well, and there are
long, springy pieces of metal to achieve an RF seal when the doors
are closed. We just call it "finger stock".

There are also 2 sets of doors. Like an air-lock, only it's an "RF
lock". It's kind of like the contstuction of a microwave oven. If the
RF got out while it was running, it would cook you while you're
watching your popcorn pop. The proper size mesh is probably more
important than sheet metal.

A con-ex box doesn't have any of this. Especially around the doors.

--- In DMCForum@xxxxxxxxxxxxxxx, Jim Strickland <ihaveanaccount@xxxx>
wrote:
> 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
>
> On Thu, 22 Jan 2004 15:41:52 -0500 "Dave Stragand"
> <dave.stragand@xxxx> writes:
> > Think "cell phone".  They work 3 stories underground in my
parking
> > garage,
> > and in elevators (metal boxes) and Lo Jack is pretty much the
same.
> >
> > -----Original Message-----
> > From: Jim Strickland [mailto:ihaveanaccount@xxxx]
> > Sent: Thursday, January 22, 2004 3:22 PM
> > To: DMCForum@xxxxxxxxxxxxxxx
> > Subject: Re: [DMCForum] Re: Lo-jack
> >
> >
> > anyone want to try to explain how the signal can go through an
> > enclosed
> > metal box?
> >
> >
> > >The signal can be received in underground parking garages and
metal
> > shipping
> > > containers.
> >
> >
> >
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