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Re: Random TC Questions

Original poster: "Jim Lux" <jimlux@xxxxxxxxxxxxx>

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx> To: <tesla@xxxxxxxxxx> Sent: Sunday, March 13, 2005 9:25 PM Subject: Re: Random TC Questions

> Original poster: "Gerald Reynolds" <gerryreynolds@xxxxxxxxxxxxx> > > The strike rail should NOT be closed otherwise it will look like a shorted > turn and kill the magnetic fields that make the coil work. > > You should connect the strike rail to the base of the secondary which in > turn is connected to RF ground (and NOT the power cord safety ground) > usually a stake in the ground, or a water pipe, etc will work for this. \

For safety reasons, the bottom of the secondary SHOULD be connected to the
"green wire" electrical safety ground. (TCs aren't well covered by the
electrical code, however, the code does require that all "things you can or
are intended to touch"  should be grounded, or, alternately, sufficiently
well isolated that no current can flow if you touch it AND a ground at the
same time)

However, you shouldn't be relying on that ground for your RF return.  For a
small coil, use a piece of chicken wire under the coil as a counterpoise or
ground plane.  What you essentially want is a conductive surface with a
radius about the same as the height of the coil above it (so, if the top of
your coil is 3 feet off the table, you want a 6 foot diameter circle.)
Nothing special about the size, though.  bigger is always better.

For RF grounds, closer to the coil is better.  A 100 foot wire to a ground
stake out in the backyard is much worse than a 5 foot square of chickenwire
right under the coil (and, that chicken wire will capacitively couple quite
nicely to the ground under it, anyway).

If you are concerned about RF currents flowing into your electrical system,
then you can put an RF choke or filter in the wire connecting the
counterpoise and the green wire ground, but make sure that the filter can
carry the current of a possible fault to the power line and that it passes
60 Hz well.  The idea is that if the AC line happens to short to the
groundplane, the fuse will blow or the circuit breaker will trip.

> EMI filter is not necessary for the coil to work.  The desirability of it
> depends on what is the surrounding environment (ie, who or what are you
> going to interfer with).  My 1000 watt coil has yet to have a line filter
> and does not interfer with the TV when on its own load panel (breaker box)
> branch.
> Gerry R.
> >Original poster: "Medina, Benjamin (UMR-Student)" <bamxbb@xxxxxxx>
> >
> >Hello Folks. I have two random questions:
> >
> >1. Is an EMI Filter between the NST primary and the power connection
> >recommended or required? This is a school project.
> >
> >2. I've seen images of the strike rail having a gap (not connected or
> >soldered). I read somewhere that there should be a gap so that the
> >strike rail does not form an inductance which may interfere with the
> >operation of the primary/secondary magnetic coupling. What happens if I
> >connect the strike rail and then run that to the ground?
> >
> >Thanks again!!
> >
> >Ben Medina
> >Rolla, MO.
> >
> >