Ok that is one scenario. Another i've theorized goes like this and I would
value your input. Say i wrap the bottom deck (containing mots, doubler, rc
low pass filter, safety spark gap, and asrsg) with wire mesh and connect
that to rf ground along with secondary base, safety spark gap, strike rail,
mot cores (in this case using copper ground rod as rf ground) near coil.
Power input wires for mots and rotary spark gap are wrapped in copper emi
tape that connects to rf ground, (only at that end!) And goes until it
meets control box (to protect against top load strikes)
Does this sound appropriate?
As an aside, I, rather optimistically, build a dual scr phase control
circuit for speed control to the asrsg that sits inside the control box.
Could I build a faraday cage around this(to protect scrs) that is
completely encased and not grounded? This would be completely separate from
rf ground scenario theorized above. The input (from wall) and output (to
rsg) both have microwave oven emi filters in line.
I have some pictures I could provide if that helps!
Thanks again!
On Fri, Oct 16, 2026, 12:39 PM Jim Lux <jimlux@xxxxxxxxxxxxx> wrote:
> Connect counterpoise to cage. There’s really no inside or outside at these
> frequencies.
>
> Sent from my iPad
>
> > On Oct 15, 2026, at 18:51, George Schramm <georgeschramm5@xxxxxxxxx>
> wrote:
> >
> > Ok, good to know on the emi filters. I'll look them up to be sure. The
> coil
> > is designed to run at 131khz, although hopefully they'd have some use
> > blocking hf (mhz) transients generated by the spark gap firing.
> >
> > As far as the faraday cage, should the inside be grounded to the
> > counterpoise, and the outside to safety ground? Or leave the cage inside
> > disconnected from the rf ground and just surrounding the coil?
> >
> > Thanks for your help!
> >
> >> On Thu, Oct 15, 2026, 3:54 PM Jim Lux <jim@xxxxxxxxxxxxx> wrote:
> >>
> >>
> >>
> >>
> >>
> >>
> >> Faraday cage or simulacrum is he way to go. You could use something
> like
> >> 4" reinforcing mesh for both the counterpoise and the walls and roof of
> the
> >> cage. Or whatever is structurally, aesthetically, etc suitable.
> >> You'd want to have that cage connected to "green wire" earth ground for
> >> safety - if someone touches it, with bare feet on floor, you don't want
> a
> >> shock.
> >> Isolated things near a tesla coil running can pick up a surprising
> charge.
> >>
> >> I'd not worry about a ground rod.
> >> RF choke on power wires is a good thing. The Corcom filters *might* be
> >> ok. You need to look up the data sheet and see what frequencies they
> are
> >> good for. If your coil is running at 100kHz and the filter is a low pass
> >> with a cutoff of 1 MHz, that doesn't do much good. Those filters are
> >> designed for particular applications - some are good for low
> frequencies,
> >> others are looking for 10s of MHz (e.g. to keep computer noise out of a
> >> power line or box)
> >>
> >>
> >>
> >> On Thu, 15 Oct 2026 12:33:00 -0700, George Schramm <
> >> georgeschramm5@xxxxxxxxx> wrote:
> >>
> >> Hi all,
> >>
> >> I'm currently building a dual mot asrsg 6" tesla coil, and i'm debating
> >> different grounding scenarios and am looking for advice.
> >>
> >> Ideally i'd like to run the coil in my garage, with a, say, 4'x4'
> >> galvanized metal roofing counterpoise, surrounded by a Faraday cage that
> >> also connects to the counterpoise, as well as the strike rail and mot
> cores
> >> and safety spark gap. The coil would be completely encased.
> >>
> >> Another option I was thinking is running a standard copper ground rod
> >> outside, no faraday cage, in this instance I was wondering if I can
> connect
> >> my mot cores to mains ground, maybe with a rf choke on the mains ground
> >> line to discourage rf from the power supply flowing back in through the
> >> mains ground wiring. Is this acceptable?
> >>
> >> The coil will run dual mot with a voltage doubler, 500pf 40kv bypass
> caps
> >> and 2x 1kohm 225watt resistors forming a low pass rc filter. Along with
> a
> >> safety spark gap connected to rf ground.
> >>
> >> I also have two 30a Corcom emi filters, one at the input of the control
> >> box, and one on the output of the 20a variac.
> >>
> >> Power input is limited with a 120v 20a circuit, (us)
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> >>
> >>
> >>
> >>
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