Re: Ground system for outside operation: Counterpoise?

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

Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>

Tesla list wrote:

> Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>
>>The larger question may be: What constitutes an adequate tesla coil ground,
>>an optimum tesla ground, and what are the characteristics of both? Then, for
>>the selected proposed physical ground arrangement--ground rod(s),
>>counterpoise, etc.--how must that ground be constructed to meet the
>>conditions demanded by the answer to the first question.

> I think that the answer for this, in what concerns the operation of the
> system, is that the ground connection shall have an impedance to the
> effective ground significantly smaller than the impedance from the
> secondary terminal to the ground, at the operating frequencies.
> This is not much. Consider the load capacitance of a small coil as
> being 20 pF, at 300 kHz. The load impedance is then:
> Z = 1/(2*pi*f*C) = 27 kOhms.
> Any kind of ground connection, resistive (ground rod) or capacitive 
> (counterpoise) with less than a few kOhms of impedance would be
> adequate.


> This is easy to verify by operating the coil at low-power, with a
> low-impedance square-wave generator across the primary gap, and
> observing the primary waveforms in an oscilloscope. With a small
> coil as described above, there is little difference between a solid
> ground connection and a finger touching the disconnected ground
> connection (of course, in the low-power test only!).


	However operation with breakout, or even full power
	sub breakout may be _different_.


	I think this is an area open for experimentation.
	Thoughts:
	There ie ALWAYS a 'ground', sometimes explicit or:
		sometimes provided by stray capacity at base
		of coil,
		sometimes, i suspect, provided by quasi
		invisible corona or spark at base 'finding'
		ground.

	The current at base may be hinger than current at top:
	If there is a 1/4 wave voltage peak at top, then there
	is a 1/4 wave _currrent_  peak at bottom.

	(I recognize my second comment is subject to debate &
	disagreement...   8)>>)

-- 
	best
	dwp

...the net of a million lies...
	Vernor Vinge
There are Many Web Sites which Say Many Things.
	-me