RE: 2 layer primary puzzle

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

Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Gary.Lau-at-compaq-dot-com>

While primary-to-secondary winding direction relationships are
irrelevant, the two layers of a primary must be wound in opposite
directions if joined in the center.  I'll try and take some photos of
mine and post them soon.

Regards, Gary Lau
MA, USA

Original poster: "James T by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jamest2000-at-att-dot-net>

Hi Everyone,
 I will keep this brief. I am working on an 8" coil with a 2 layer
primary.
I have constructed the primary and
it is not behaving as I expected. I measured the inductance of the
primary
by itself.
  What happens is, I measure from the outside of the top coil to the
inside
and the inductance goes up as
expected. Then I drop down to the bottom layer and measure from the
top/outside to the bottom/turn, oops, the
inductance goes down as I go out. The inductance of the bottom coil
seems
to cancel the inductance of the top
coil. Please set me straight on this.
1.understanding/myth - the winding direction between the 2 coils is
irrelevant.
2. understanding/myth - the "mutual inductance" of the 2 coils increases
inductance, not cancels out the
others inductance.
3. 2 layer primary's are a practical approach. I seem to recall some
posts
on this, and it was considered
reasonable. Brilliant to ask now that it is done!
Any comments will help. Thanks,
 James Cart