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Re: More tube coil stuff (Carl Willis)...
In a message dated 9/1/00 11:23:35 AM Pacific Daylight Time, tesla-at-pupman-dot-com
> Original poster: "David Trimmell" <davidt-at-pond-dot-net>
> Hey all Tube types, Have many found the "Under" the primary grid coil to
> "superior" to placing it "over" (on top) of the primary? This is mostly in
> regard to solenoid type primaries, as I have found that "usually" (in my
> limited tests) flat spiral primaries seem to like feed back coils on the
> top (again, I may have missed something).??
I've compared the operation of my small Tube TC (20" sparks) using
both over and under positions for the grid feedback coil. I didn't see
any difference in performance either way. But I now prefer to put
the grid coil under the primary to prevent arcs from jumping to it
from the top of the secondary at higher powers. This all refers to
solenoidal coils. I never got good results from my VT-27 tube coil
with the flat pancake primary, although the larger tube coils that
gave up to 38" sparks gave excellent results with a flat pancake
primary. In this coil, the feedback coil was at the center of the flat
pancake, and the feedback coil was a two layer solenoid.