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I'm writing as a new member to the list... I started coiling about two
years ago, building a small "table-top" coil with a 15000/30 NST and
2.125" x 12" secondary w/ #28 ga. wire. Anyway, I started reading the
archives a few months ago, beginning with Jan. '98, to get a little
perspective. I finally caught up, and have nothing to do now but join.

Reading the list has been informative, but now that I'm current, I
figured the best course of action is to start experimenting so that I
will have something to say. I have a design element to share, and some
questions. My new design idea came about when I read a post a few months
ago about parasitic oscillations occuring between the capacitance and
self-inductance in a rolled-PE cap. if these caps have inductances, can
they be designed for a specific frequency? then it hit--maybe I can
build a combo cap/primary by rolling thinner strips of foil around a
large form  (just large enough to fit over a secondary) and connecting
them on opposite ends (as the opposite charges move toward opposite ends
of the plate, their inductances add). Just last week, I saw a post by
Terry Fritz musing about the same thing. I decided to try it. I set the
plate area and no. of turns based on my current coil, trying to match
the capacitance and no. of turns of my coil at resonance. I wound 2  8'
lengths of 6" wide foil separated by 4 sheets of 4mil PE on a 7" dia.
form. I used a 9kv 30ma neon  with primary in series with another to
keep the power low (nothing in oil, yet) and placed my grounded
secondary in the center of the pri/cap. The sparkgap (a mini-RQ-style
gap) was in parallel with the power supply and cap/primary unit.  to my
surprise and enjoyment, I got about 1" to ground off the top of my
secondary. (to keep perspective, I tried the same power supply
arrangement on my conventional setup, and got about 3"  at tune) so I'm
seeing 1/3 the usual output on a blind guess--I don't even have a way to
tune it yet. I plan to build a model to withstand usual TC voltages, and
with a few design improvements: a few taps on the outer end of the roll,
to vary the inductance, and a sturdier design. I will probably add a
single turn of copper pipe around the outside, for continuous tuning.
And of course the whole thing will have to be put into oil and pumped
out. 
I think the major advantages for such a system would be high Q for the
tank circuit- the sparkgap could be situated very close to the leads to
the plates, and with no caps to charge away from the primary with leads,
etc. The current would be simply kicking from plate to plate through the
gap (while it is conducting, of course) I also think that for the
dimensions of such a coil/cap, that it would lend itself well to
magnifier design, ie wrapped on top of a driver secondary. Thus my next
project, and a few questions...
I am planning a magnifier design with the pri/cap unit, a rotary gap,
and a DC power supply. Due to my living situation (one-bedroom apt.--I
can feel the whole list wince) I am limited to table top coils. It gives
me the opportunity, however, to concentrate on compactness, efficiency,
adjustability, and innovation, as well as pulling max.  spark length
from a fixed power source: Aforementioned 15,000/30 NST. Anyway, I have
20 square feet of copper foil I picked up at a metal surplus place, and
some diodes on order (sourced from the list--thanks) but I haven't built
a rectified power source before, and could use some hints, and things to
watch. While I was in the surplus place, I checked out an odd-looking
transformer--the plate says it is a GE Current transformer with a 200:5
ratio. Judging from the shape-- like a thick cylinder with a hole in the
center-- it goes onto power lines, perhaps to measure current? This
would mean it is just one coil within the rubber housing--could this
have any  TC use? could I insert a primary and core into the tube for a
homebrew trannie? could I use it as an adjustable ballast with a movable
core?
But I ramble on...anyway, back to work.

Wells Campbell