[Towertalk] RE: which box to use ?

[Dan Hammill]

Agreed.  If I remember my college electromagnetics, ANY fully enclosed
metallic containment constitutes a Faraday shield - all the charge is on the
outside, zero on the inside.  Now, if you add openings, that's a whole
different story.

The screen rooms I use at work are all made out of copper screening.  Lots
of RF and junk on the outside, very little on the inside.  Definitely not a
ferromagnetic material.

I once made an anechoic chamber out of plywood sheet covered with 0.002"
Aluminum furnace tape.  Better than 90 dB of inside-to-outside attenuation
at 18 GHz.

Dan  KB5MY

> -----Original Message-----
> From: towertalk-admin@contesting.com
> [mailto:towertalk-admin@contesting.com]On Behalf Of Norman Hockler
> Sent: Monday, September 02, 2002 17:15
> To: Towertalk@contesting.com
> Subject: Re: [Towertalk] which box to use ?
>
>
>
>
> Unless they changed the laws of Physics while I was asleep last night
> Aluminum makes a wonderful Faraday shield.
>
> Norm N8NH
>
>
> At 03:05 PM 9/2/02 -0400, you wrote:
> >It's a no-brainer:
> >
> >Metal - and steel at that.  Aluminum will not do the following:
> >
> >With steel, you get the benefit of Faraday shield that you will
> not get with
> >plastic or with aluminum.
> >
> >All cables (coax, rotor, other control cables, even CATV, TELCO, etc.)
> >should go through a hole in the SPG metal box, and thereby through the
> >Faraday shield.  This will protect from H and E plane energy
> that builds-up
> >on the cables en-route to the SPG box.  The box itself should be
> grounded to
> >a ground rod via a very low-inductance ground, such as a copper strap
> >located directly below the SPG.  In the case of a SPG box that's rather
> >large, or if you want more protection, ground the box at the leading edge
> >and trailing edge lower corners.  The leading edge is a reference to the
> >route that the incoming ground wire (from the tower or
> ground-grid) takes to
> >the SPG and the direction the outgoing ground wire (to the rest of the
> >ground-grid) takes to/from the SPG.  See my website for my example:
> >www.erols.com/n3rr
> >
> >73,
> >Bill Hider, N3RR
> >
> >----- Original Message -----
> >From: <KB2HUK@aol.com>
> >To: <towertalk@contesting.com>
> >Sent: Monday, September 02, 2002 12:01 PM
> >Subject: [Towertalk] which box to use ?
> >
> >
> > > <PRE>Hello everyone !  I need some advise.  I am terminating
> all my runs
> >of coax
> > > and rotor cable into a box which has the correct poly phayser
> suppressors
> > > installed in a length of 1/4 inch thick buss bar. the coax
> will then come
> >out
> > > of the surpresors and into the house.  my question is this I
> am planning
> >to
> > > enclose this junction in a box I want to know which would be
> better to use
> >a
> > > metal electrical box or a plastic non conductive box like the new tool
> >boxes
> > > ?  I have both . thanks for your input !     John kb2huk
> > > _______________________________________________
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> _______________________________________________
> Self Supporting Towers, Wireless Weather Stations, see web site:
> http://www.mscomputer.com
> Call 888-333-9041 to place your order, mention you saw this ad
> and take an additional 5 percent off
> any weather station price.
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