Re: grounds, was RE: capacitance of homemade caps

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Karl Lindheimer <karl@xxxxxxxxxxxxxxx>

Paul,

A counterpoise ground consists of material like chicken wire or metallic 
window screen.  It should be sized so that it's diameter is at least as 
tall as your secondary.  Larger is better.  It is placed directly under 
your coil, and the bottom turn of the secondary is connected to it.  It 
works by capacitively coupling to the underlaying material and providing 
your secondary with a return path.

It sounds as if your current ground system is more than adequate.  You 
could try your coil with the ground rod only, then add a counterpoise and 
compare performance.  Another experiment would be to ground your 
counterpoise screen to the ground rod, and compare as well.

Basically, a counterpoise ground system is used when it would not be 
practical (or possible) to connect your coil to an earth ground.  Coils 
running on the third floor of a large building, would be perfect candidates 
(for example.)


Best Regards,

Karl

On Apr 8, 2005, at 11:06 PM, Tesla list <pbbrodie@xxxxxxxxxxxxx> wrote:


> So, after reading your post, I'm a little confused about grounding my 
> small coil, 15 kV, 30 mA NST, 4" diameter by 21" tall secondary. I have 
> driven an 8' by .5" ground rod approximately 10' from where I plan to run 
> the coil, the front part of my garage on a concrete slab. The bottom of 
> the secondary is connected to this ground rod by 10' of two 15' long auto 
> jumper cables, four conductors of 4 AWG.
>
> I asked this question once before with no responses. Should I use a 
> counterpoise ground? Can someone please explain how a counterpoise works? 
> Is a counterpoise an either or proposition or should I use both? Thanks. I 
> really appreciate any help.
> Paul Brodie