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>

(Much excellent comment made. A few added thoughts.)

>I'm sick of waiting for a somewhat warm calm night to

>fire my coils.  I am also tired of trying to get my

>father away from home because of his pacemaker.

         Oooookay.  Serious Faraday Cage wanted.
         Serious attention to seem bonding.
         Coils can radiate at harmonics, etc, well
         away from (up from/shorter than) fundamental.

  I am now building a Faraday cage in the basement.  It will
>be 10' X 10' X 7' and be built out of 3/4" Cu pipe

         If this is for frame, little need, tho it won't
         hurt.  Wooden frame is fine, so long as edges of
         pieces of shield are joined/bonded to each other.

>and chicken wire, with a 1/4" hardware cloth roof.

         ...and The Floor?
         (as was quite properly asked....)
         (mesh under masonite, or equivalent works....)
         ...and bond the floor edges to the wall bottoms.

>Other than the door which will be caged,

         To be effective at 'all' freqs, the door edge
         must be finger stocked.  For coiling freqs this
         is less critical, however, if done, it will help
         keep the Upper Harmonics inside.

>there will be two ports, one 6" X 6" port for cable

>passthru,

         Must be filtered, as noted, to be effective
         as Faraday cage (keep the noise in).

>and one 6" X 6" camera port.  Grounding will be made by

>a 8' copper ground rod, and 3 strands of # 6 bare ground

>wire.  The 8' rod will hit lake level during the summer,

>but the lake level drops about 1 1/2' in the winter.

         Concur with previous comments:
         The inside IS the 'ground'  tying it to 'real
         dirt' (except for primary side safety ground)
         is irrelevant.

>The top of the rod will be monumented with a concrete pad

>so I don't hit it with a lawnmower.  I am thinking of

>adding a separate RF ground for the coils.  Is this

>separate RF ground okay?
         Connected to what?

         I would expect coil bases to be tied to the inside
         of the shield box.
         (when doing this sort of work:
         Must always be able to say:
                 THIS is the inside.
                 THAT is the outside.
         And know what is tied to what.

===================================================
         It is perhaps useful to say that a cage can be
         assembled, to make what might be called a
         'strike box': something to keep the sparks in,
         and be handy and useful for that task.  It might
         lack a formal metal floor.  It need not be a
         _Faraday_ _Cage_ to do that.

         IF all the edges, including the door edges be
         bonded and ALL the lines in and out be filtered,
         and the floor bonded in, then it can ALSO function
         as a Faraday Cage, to keep the EMI/RFI in...

-- 
         best
         dwp

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