mini coil primary coupling ?

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

Original poster: "Laurence Davis by way of Terry Fritz <teslalist-at-qwest-dot-net>" <meknar-at-hotmail-dot-com>

I'm near to complete the mini coil.  I've decided to make a conical 
primary, since i've heard they
are more efficient for a small coil.  I'm aiming for a coupling of 0.18, 
which i thought I had heard was optimal.  all other conditions fixed and 
assuming a 'tuned' state, changing the primary spacing or
primary angle should only change the total output by about a 25% variance 
(lets say coupling is a fixed variable as well).  Am i correct?  I've read 
that there is a preferred ratio from primary width to secondary 
height.  Why this relationship?  em field size of the primary compared to 
the secondary?

larry.