Re: Longest practical ground cable?

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

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

Tesla list wrote:

> Original poster: "Garry Freemyer by way of Terry Fritz
><twftesla-at-uswest-dot-net>" <garry-at-ndfc-dot-com>
 
> What's the longest RF ground cable I can have?

	As short as possible....
	(helfpul_not   8)>>)
 
> I've been thinking maybe I could drive a rod on the edge of my porch.
> Trouble is, the thing is 30' away. That seems to be too long.

	Longer than optimum.  Arguably acceptable for Tesla work.

> With ham radio, if I remember correctly, the ideal ground cable has
> to be shorter than a quarter wave

	MUCH shorter.
	A wire (exactly) 1/4 wave long will have a current peak at one
	end (typically ground) and a voltage peak at the other.
	So 1/4 wave will look like an open circuit to the RF.

> of the frequency you are transmitting on or it could act
> as an antenna.

	ANY ground of any length will act as antenna.  The longer the
	more so.
 
> I'm assuming it's the same with TC's

	sort of....
	The difference is that (typically) Tesla Coils are around
	100KHz (ok, VERY around....).  Doing a few approximate
	numbers:
		144KHz looks like a 500 ft 1/4 wave.
	Call it 750 ft at 100Khz, scale to suit the freq of the
	coil in question.  30 feet is reasonably short.  Off Hand,
	Multiple grounds are mote important than length, IF the length
	is that short...

	(Someone check those numbers, in case i dropped decimal...)

	best
	dwp