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On 11/5/14, 2:39 AM, John Cooper wrote:
Yeah I have to cut my copper tubing and just bring the gto wire up to
it instead. Easier than redrilling and inserting bushing of some
sort. The grounding wires ( bottom secondary, nst ground, strike
rail) that goto the ground rod I'm planning on using #8 thhn I had or
does that have to be gto wire too?
Bare wire would be ok.
#8 is massively overkill. You're not carrying the kind of current that
would need that large a conductor.
As is a ground rod, really.
You want the RF current and "strike current" from sparks to return
easily to the base of the coil, so the optimum strategy in general is to
have a large conductive plane or counterpoise directly under the coil.
Think of this plane as forming "the other plate" with the topload
capacitance. And, it's a place where sparks that terminate at the
ground (or near) will touch, rather than somewhere else.
Large in this case would be a radius comparable to the height of the
topload above it. So if you have a table top coil that's 3' high (from
tabletop to top of secondary toroid) then a 6 foot diameter sheet would
be adequate. It can be solid, or chicken wire, or hardware cloth, or
radial wires or anything, as long as it's low resistance. If your coil
stands 6 feet high, then a 12 foot diameter circle, etc.
That counterpoise should be connected to the electrical safety ground
(greenwire ground) so that if you touch it, you don't get a shock,
especially if some primary HV or line voltage carrying conductor touches
it. In particular, if a spark from the secondary happens to touch both
the counterpoise AND the HV on the primary, you've now got a fairly low
impedance path to carry line frequency current to the counterpoise.
If you're running your coil outdoors, then, sure, connecting to earth
ground as a counterpoise, directly under the coil, works. And if it's a
shortish run (a few feet) for positioning convenience, that's great too.
However, running a 100 foot ground wire from coil to ground rod/stake
doesn't do you a lot of good. And may actually aggravate RFI problems
by forming an antenna that radiates the energy from the coil