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Correctely ground a TC

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LAN_403

Unleashed

Thu Jul 12 2012, 04:06PM

Registered Member #5171 Joined: Tue Jun 05 2012, 11:32AM
Location:
Posts: 67

Hello everyone.
Sorry if i'm opening so many threads so far, but since it's my first TC, i really need to know lot of things, so please be patient :)
My question today is
How to correctely ground my tc?
I mean, my home power plant, has no ground, so i can't do it by just setting it on the middle pin of the socket.

What i wanted to do, is grounding it by planting a steel bar( like one of those

) in the ground, and maybe give it some salt water.
But someone told me that at high frequencies some material becomes bad conductors.

So, how should i ground my TC?
Thanks.

Tetris

Thu Jul 12 2012, 05:22PM

Registered Member #4016 Joined: Thu Jul 21 2011, 01:52AM
Location: Gainesville, FL
Posts: 660

I use a copper pipe, about 5 feet in length, 4 feet I was able to bury into the ground. If it hasn't rained in a while (saying you live in Italy, in a Mediterranean climate, drought should hardly be a problem), say, a week or so, then I suggest watering it with a simple garden hose. :D hope that helps.

Patrick

Thu Jul 12 2012, 06:48PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

At high frequency the cross section of the conductor starts to effectively shrink, due to skin effect. And the conductor acts as if it were a hollow pipe at HF, (even if its a solid rod). But i think for TC use as highvoltagechick said, use a copper water pipe, it seems to work for many people just fine.

Unleashed

Thu Jul 12 2012, 07:46PM

Registered Member #5171 Joined: Tue Jun 05 2012, 11:32AM
Location:
Posts: 67

I have bought a 1.5meters grounding rod.
But.. it'll be hard to plant it in the ground :P It's like 40Â°C and doesn't rain since a month or so...

Patrick

Thu Jul 12 2012, 08:02PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

start pounding.... some electricians use a tiny jack hammer-like device thats meant to drive the longer rods in.

Dr. Slack

Fri Jul 13 2012, 07:13AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Sigh, I see so much BS talked about coil grounding.

Why do you want to ground your coil? Electrical safety, like able to blow supply fuses in the event of short circuit, or RF performance?

If you want RF performance, which includes reducing emissions to to other parts of the house, then you need something approximating to an RF ground plane *immediately below the coil*, connected to the bottom of the secondary. An RF ground plane could be a large sheet of solid metal, or large sheet of chicken wire, or several straight wires fanning out in a radial fashion from the middle. If you are running it in a field, put a wire down from the bottom of the secondary to a teaspoon or tent-peg stuck in the ground. The currents are so low, the impedance so high, that that is enough.

If you want safety, then additionally you connect the earthy bits in your primary circuit back to mains ground. If mains ground is not available, then you pound a 6ft pole into wet ground, and/or put croc-clips to all the metal pipes that you have buried in the ground. The currents required are so high, the impedance so low, that you need all the help you can get.

Neither grounding system depends on the other. Neither grounding system will do the job of the other.

brandon3055

Fri Jul 13 2012, 08:16AM

Registered Member #4548 Joined: Mon Apr 23 2012, 03:52AM
Location: tasmania
Posts: 271

For my.latest tc build I use manes ground for safety and for the rf ground I just have a wire from my secondary to my shed and it seems to work ok what is you opinion on this method

Dr. Dark Current

Fri Jul 13 2012, 09:57AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

I have ran coils with sparks up to 60cm (24") grounded to mains ground. Put some caps a few tens of nF from live and neutral to Earth.

Sigurthr

Fri Jul 13 2012, 11:38AM

Registered Member #4463 Joined: Wed Apr 18 2012, 08:08AM
Location: MI's Upper Peninsula
Posts: 597

Dr. Slack wrote ...

Sigh, I see so much BS talked about coil grounding.

Why do you want to ground your coil? Electrical safety, like able to blow supply fuses in the event of short circuit, or RF performance?

If you want RF performance, which includes reducing emissions to to other parts of the house, then you need something approximating to an RF ground plane *immediately below the coil*, connected to the bottom of the secondary.

Being a Ham I fully agree and understand the importance of a proper ground plane grounding system when dealing with most RF sources, but I have a practical question for you: How do you stop the ground plane from sapping energy out of the system due to induced eddy currents from the Primary's magnetic field? I tried a similar setup using a large sheet of steel under the coil and got zero output from the secondary and the ground plane got VERY hot very fast. I tried increasing the vertical distance between the tesla resonator and the ground plane but could not achieve a set up where the ground plane was not badly drawing energy from the coil, even if heating was reduced below perceivable levels.

From my experience a ground plane is good in theory for a TC but bad in practice.

Dr. Dark Current

Fri Jul 13 2012, 12:11PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

I think the frequencies of normal TCs are so low (few hundred kHz), that a ground plane is not necessary.

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