Flat Primary Winding - next question

From:  Steve Young [SMTP:youngs-at-konnections-dot-com]
Sent:  Monday, June 15, 1998 7:51 PM
To:  Tesla List
Subject:  Flat Primary Winding - next question

To all who responded to the "Round vs Flat Primary Winding" thread, thank
you for the interesting and insightful comments.

The consensus was a primary wound with flattened copper tubing or strap
would provide more inductance per given coil diameter, or smaller coil
diameter per given inductance.

On the latter point, (more compact primary), I am wondering just how
primary diameter affects coupling to the secondary.  I envision the
magnetic flux from a larger diameter primary will intercept more of the
secondary than will a more compact primary, but I don't know the practical
significance of such an effect.  I would assume we should couple to as much
of the secondary as possible to even out the secondary volts per turn
distribution (implies large diameter primary).  But large diameter
primaries probably exhibit more losses.  What are the factors to determine
the "best" primary diameter for a given secondary & torroid?  Comments?  (I
know--I opened up another opportunity for John to pitch his JHCTES

This leads to another thought.  If the primary effectively couples mainly
to the lower part of a 1000 turn secondary (e.g. the first 100 or so
turns), then do we in effect have a 100 turn secondary feeding a 900 turn
third coil?  In other words, does a conventional TC function as a merged
combination of pulse transformer and magnifier extra coil?  I envision the
transition zone from conventional two-coil TC to magnifier extra coil would
be a gradual effect, depending on how the primary magnetic flux was shaped
and intercepted the secondary.  I suppose the answer to this probably
doesn't affect how to build decent coils, but perhaps it could lead to
better understanding of how our beloved TCs actually do their thing. 

Lastly, wouldn't it be interesting to actually map the magnetic flux
between primary and secondary (and floor and whatever else) to better
visualize how concentrated or distributed the magnetic coupling actually
is?  I have seen posts which suggest the visual purple air ionization
visible between primary and secondary has something to do with magnetic
coupling.  I believe the effect is purely high voltage ionization of air
and is not an indicator of anything going on magnetically.  Comments?

Thanks in advance for responses.