Re: [TCML] Safely Grounding a Tesla Coil

[mddeming@xxxxxxx]

Hi Brandon,
 
 In a nutshell, a counterpoise is a large radial array or screen, insulated from the ground but close* to it, to serve as a capacitively coupled ground. It was developed for use where soil was too poor for a good ground connection. This was the term as used in antenna theory texts between ~1920 and ~1950 and is still the way coilers use it. In recent years, the term has been bastardized in antenna books to include any and all elevated radials on a monopole antenna.[1] Of course, for an antenna whose function it is to radiate energy, a much larger counterpoise is necessary. For a TC it is adequate for the diameter of the counterpoise to equal the overall height of the coil.
There are several ways to make one for a TC: The quick and dirty Type 1 is just a large disk of aluminum foil glued to a board or sheet of cardboard. Type 2 is copper window screen. Type 3 chicken wire. Type 4 radial wires laid out like a "daisywheel" print head[3]. Type 1 is the easiest to make, type 2 & 3 more expensive and harder, but lower eddy currents, type 4 the hardest, but has the least eddy current losses.[2]
 
Matt D.
 
[1] http://www.antennex.com/shack/Dec06/cps.html
[2] Bylund, Duane - "Modern Tesla Coil Design Theory"
[3] http://en.wikipedia.org/wiki/Daisy_wheel_printer

* close in terms of a tiny fraction of wavelength




-----Original Message-----
From: Brandon Hendershot <brandonhendershot@xxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Sat, Feb 6, 2010 12:10 pm
Subject: Re: [TCML] Safely Grounding a Tesla Coil


Hi Jim, 
 
Could you explain the concept of "counterpoise" for me or provide a link to some documentation? I've never heard of anything like it... 
 
Thanks btw, 
Brandon 
 




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