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Re: which ground is best if you can't use RF?
Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>
For a small coil, the best all around indoor solution is an artificial
ground plane or counterpoise that serves as the RF ground. 4x4 square feet
of chicken wire would serve admirably for a 2 foot high coil. That way,
all the RF goes into your chicken wire and the coil, and relatively little
is coupled into water pipes, ground wires, etc. etc.
Standing waves for the fundamental frequency are unlikely, even with a long
wire... The wavelength at 300 kHz is 1000 meters, so unless your wires are
on the order of 250 meters long, then it's not much of an issue. Granted,
higher harmonics could have significant power,and form standing waves..
The idea is to not try to run RF through long wires at all: they just act
as an antenna and potentially make things worse. Give it a close and near
at hand ground to work with: a counterpoise...
The radiated energy from the actual sparks is more impulsive in nature, and
has significant components much higher in frequency, and for that, the
physically short connection is important, because you want to make the
"area of the current loop" as small as possible. A spark going 2 feet from
the top load, to a RF grounded rod then down 3 feet to a counterpoise is
only an area of 6 square feet. Compare this to some scheme where the spark
goes to a free air then capacitively couples to the groundwires in your
walls, then to the electrical panel then to your panel safety ground, then
to that ground rod out in the yard, and finally back up that 50 foot ground
wire. Lots of possibilities for electromagnetic radiation, voltage drops,
arcing, etc. all along that path. This is another reason not to fool with
50 foot long ground wires, cold water pipes, or stuff of that nature.
General guideline for counterpoise size: radius = height of topload above
>----- Original Message -----
>From: "Tesla list" <tesla-at-pupman-dot-com>
>Sent: Wednesday, January 08, 2003 3:59 PM
>Subject: which ground is best if you can't use RF?
> > Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>"
> > Hello, i will be running my coil at school (lots) and the room where i
> > be running it in is far away from the outside. Which would be better.
> > the ground plug in the wall, using cold water pipes (plenty of those), or
> > running a 75' cable (or longer) outside.
> > Thanks
> > Adam
> > P.S. Aol has reccently decided to deliver my tesla mails, how come it is
> > working now?