Re: Faraday Cage

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

Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>


>I forgot about the floor, but I have enough chicken wire

>T/G 3/4" plywood to put a floor in.  The concrete floor

>does have reinforcing mesh in it though.

         Irrelevant, since it can't be tied to the cage wall.

>I chose to use a separate ground rod for the cage,

         Can't hurt, but irrelevant.

>(too many weird things happen on power ground) power ground

>  will only run up to the variac in my controller and from

>that point everything else is on RF ground.

         The RF ground is the inside of the cage.
         The RF ground is the inside of the cage.
         The RF ground is the inside of the cage.
         The RF ground is the inside of the cage.
         The RF ground is the inside of the cage.
         (this is not negotiable....)

         IF the wire to the external ground pipe is
         tied to the cage wall, well tied, then it
         does no harm.
         If the wire to the external ground pipe is
         run 'through' (insulated) from the cage wall,
         then the cage is useless, pointless and
         defeated.  (except as a sparks box).
         Been There, Done That.
         This is physics, not subject to negotiation.

>I don't think the cable passthru will be much of a

>problem

         It Will.
         Period.
         Been there, Done That.
         Any Insulated, Unshielded, Unfiltered Conductor
         Going Thru Will Carry Stuff Out.
         (Any given installation may luck out.  Or
         May not.)

>as the controller will be sitting only 1" away from the

>cage with the connectors protruding into the hole.

         Must be a metallic, bonded, filtered join.
         The RF wavelengths of the power sparks are long
         they may be contained:
         There is SUBSTANTIAL energy All Over The Place,
         including VHF.  This WILL ride out on the any
         unfiltered, insulated lines.
         Been there, Done that.

         (it was 'work'.  We had a spectrum analyzer & could
         'see'.)

>The variac output and SRSG outputs will both be filtered.

         THAT's Better.  Filter MUST be 'in' the cage wall
         (to work well).  Old EMI Engineer taught me this:
         Picture the rf trash as flowing down the wire.
         It comes to a 'wall'.  Unless the filter is bonded
         IN the wall, the trash radiates AROUND the filter.
         (He learnt his trade controlling SCRs on 3kvdc,
         3000 amp Railway circuits...  WE weren't working up
         there, but he had.)

-- 
         best
         dwp

...the net of a million lies...
         Vernor Vinge
There are Many Web Sites which Say Many Things.
         -me