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Re: Random TC Questions

Original poster: "Gerald  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Jim,

Do you really think that tying the strike rail and secondary base to the green safety wire is going to make the TC any safer?? If you think you need a strike rail then I'll let you touch the strike rail or base during operation. If you tie it to the green safety wire then any strike to objects earth grounded will cause the return current to come back thru your house wiring to find its way back to the base of the coil. That could kill your computers plugged into the mains even if turned off. If you think this is a code issue, then this has got to be an issue of "can touch" and certainly not "intended to touch". Then what do you do about the top load??? That can be touched too. You, as operator, have the responsiblility to see that it is not.

If the green safety wire is used to ground the TC (like for indoor operation where an earth ground is not close at hand) then, as you say, a counterpoise will be necessary to intercept any strikes and allow its return current (and RF return current) to go directly back to the base and not thru the house wiring.

Gerry R.

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