Re: Over-coupled or under-insulated?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Stephen Conner by way of Terry Fritz <teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>

At 10:14 18/03/03 -0700, you wrote:
>Original poster: "Paul Nicholson by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>
>
>
>
>Try using a mesh groundplane directly beneath the secondary.  Forget
>the sink - keep the RF contained within the direct vicinity of the
>coil.   Efficiency will be higher, interference lower, and less of
>a fire and safety hazard.

I would second that. The inductance of your coiled-up ground wire is 
probably pretty high too, which I think might cause some kind of oddball 
resonant mode that might be responsible for the racing sparks. The ground 
connection needs to be short.

On my 3.5" x 20" coil I use a few old pieces of wire mesh as an RF ground. 
I believe they were anti vandal screens from windows, but chicken wire 
works great too. The total area of mesh is about 2 square metres and it's 
located on the floor directly underneath the coil. I connect the mesh to 
the secondary and strike rail, and also to a cold water pipe for luck ;) 
I've run this setup at almost 1kW and produced 30" sparks with no problems. 
With my old 10/25 NST power supply, I never even bothered grounding the 
mesh to the water pipe.

Steve C.
http://www.scopeboy-dot-com/