toroid dimensions

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Johnson, Jeffrey D -at- PWC by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jeffrey.d.johnson-at-l-3com-dot-com>

Hi all,
Is there an optimum physical size for the topload terminal?  I bought some
4" dryer duct planning on making a 22" total outer diameter toroid for my 6"
x 24" secondary (27.5mH).  Using a 15/60 NST, a 10.5 turn .4" spaced 3/8"
copper tubing primary (56.9uH).  The topload capacity should be 23pF
(WinTesla) giving me 164.6 kHz res freq.  I've read descriptions of other
coils similar to mine with and I'm concerned my toroid may be too small.  Is
there a way to measure its capacitance?  I have a signal generator and scope
at home.  I've read about using a "grid dipping" method to measure primary
and secondary resonant frequencies for tuning.  Maybe you could measure the
secondary without toroid and then with to deduce topload cap.  Anyone tried
this?

Jeff Johnson