Re: RF ground in an apartment.

Steve wrote:

On Tue, 22 May 2007 09:59:14 -0400, default <default@xxxxxxxxxxxxx>
wrote:

On Tue, 22 May 2007 01:52:46 GMT, Steve <skamego@xxxxxxxxxxxx> wrote:


So, if the cage itself is connected to power ground, which in my case
is AC ground, as long as all wires going in and out are filtered
properly, there should not be any RF present on the ground wire?

That makes sense.

Just to clarify, how do I properly decouple the wires going through
the cage? I'm used to seeing feedthrough capacitors in RF equipment,
something along this principle? I'm having some trouble figuring out
which ground is acceptable to connect where, but I will do my
research, and likely put this project on hold until I have a more
acceptable location.

Yes feed through filters are good for this - cap and inductors in one
device. The NEC power cord filters one sees on computers and such may
work well. Switching power supplies are up in the TC coil range these
days, so those types of filters may work.

A device used in auto radios of old (50's) was something called a
"spark plate" (had nothing to do with sparks). It was a piece of mica
(high dielectric constant, low loss) on the outside of the chassis
often with a rivet or bolt carrying the battery connection to the
outside world, and a square piece of copper. Only a few pico farads
but very effective for high frequency noise. The chassis formed one
side of the capacitor and the copper the other (somewhat harder to
make safe with mains voltage).

I assume it got the name "spark plate" from auto mechanics that
accidentally grounded the hot copper piece exposed on the outside of
the chassis.

I've used that idea to decouple gunn diodes used in radar jammers.
Solder a nut to the thin pcb material and it decouples the power and
provides an isolated mount for the diode. (gunn diodes won't
oscillate if the voltage lead has inductance).

Interesting, I"ve never even heard of them.

So, if I decide to change gears completely, lose the Faraday cage and
ground plane altogether and put in a proper RF ground, I assume the
same filtering still applies to the mains wiring to keep RF out of the
115V supply, it just won't be connected to a cage? I will probably
put this project on hold until I have the proper facilities, at which
point I'll do the proper research and figure out how to do it right.

Thanks to everyone for their help, I think this will wait until a
later day.

Steve

You would still need the cage with any scheme where the coil is operated in
your apartment, both for radiated interference and to stop an arc from just
directly hitting your light fittings or wires in you walls - that would
cause some conducted interference!

Chris
.

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