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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