Re: Faraday cage

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>



> 
> I've never seen aluminum screen ignite, but I that doesn't under any circum-
> stances mean that it never would :-) "I" use the  "poultry screen wire"
for my
> Faraday shield in my shop. It's not a Faraday "cage" in that it does not com-
> pletely surround anything, it is just a "shield" between yours truly and the
> 8 to
> 10 ft power arcs that spew from my pole pig  coil :-) 13 ft. is about the
> maxi-
> mum distance that I can seperate myself from my coil in my small shop and
> with occasional 10 ft. + sparks even in a claustrophobic 12 X 24 shop build-
> ing, that's obviously WAY TOO CLOSE for comfort without a grounded shield.
> The poultry screen wire (chicken wire) is available at most home improve-
> ment warehouses (Home Depot, Lowes, ect).

I'd second the idea for poultry screen.  The other thing you could use is
the welded steel mesh used for fencing and for concrete reinforcement.
You're not going to really be making something that is RFI proof (that's a
pretty big chore), but what you're trying to do is to get the currents to
flow somewhere "safe" (as opposed to your house wiring, the aluminum foil
backed insulation, the garage door opener, etc.).  Just controlling the
"return current" will greatly reduce RFI, because you've made the "antenna"
smaller (or, more to the point for these frequencies, you've made the area
of the radiating current loop smaller).


The other big advantage of operating in a screen room is that the
electrostatic fields will be much more controlled and even, so tuning will
be easier and less subject to stuff moving around.  Basically, if you put
the TC in a grounded cage, things outside the cage won't affect the tuning.
As Brian Basura mentioned, no interference is noted with electronic
equipment inside his cage, which greatly resembles a giant bird cage (the
bars are something like 4-6" apart as I recall)..



> 
> I think it would. Since installing my Faraday "shield", I never experinece
> the
> typical RF burn/shocks from touching grounded metal objects since the
> shield is obviously between me and the spark spewing monster, even
> when I'm cranking 7 to 8 kVA :-) Now if I'm dumb enough to step on the
> business side of the shield, then that' a different story ;-)


Exactly... outside the cage, the stray capacitance effects are greatly
reduced, because the field is contained mostly in the "topload" to "cage"
volume.

> 
> << 3.  Any construction tips? >>
> 
> I think you've got the right idea. Just make sure that your 1X2 wood frame
> is sturdy enough that it want bent or break since a 6 ft. cube would be
> pretty big for 1X2s. Bracing your 90 degree corners with 6" "L" brackets
> would probably sturdy it up pretty good for you.

Gusset plates or joist hangers/connectors might be a useful choice.
>