Hello David, Jim,
...was having exactly the same concerns about corona, as you're
describing. But I had no problems at all, using the copper-ribbon
primaries:
http://home.datacomm.ch/m.schraner/FlatPrim_1555.jpg
in my UBTT Twin ( http://home.tiscalinet.ch/m.schraner/UBTT-Betrieb.pdf
), together with a 15kV NST. The Ribbon is only 0.5mm thick, and 20mm
wide (0.0197" x 0.787"). No corona was observed, however it would need
to be operated in total darkkness, and without secondary discharges, in
order to really observe it. I "think" the multiple winding effect, which
you characterize in:
"...With, for instance, 1/4" OD tubing, the radius is 0.125, so with
20kV from the NST on it, you have 20/0.125 = 160 kV/inch. While more
than double the breakdown in air, most people don't have a big problem
at that voltage (probably because having adjacent turns close by with
a voltage that is a few kV different makes the overall field "smoother".
is helping indeed. Even the taps, on the narrow spaced turns (only 6mm /
0.236"), didn't provoke any flashovers.
Well David, perhaps the idea to scrap the .022" idea could be thought
again, especially if having a multiturn primary?