Reg Edwards wrote:
The coil resonates at a different frequency which
depends on the length and diameter of the coil as well as on the
length of wire.

Yes, that's why inductive loading is more efficient than
linear loading. The inductor has the advantage of adjacent
wire flux coupling. However, the farther away in space that
a particular coil is located from a reference coil, the lower
the coupling. I just issued a challenge to anyone to prove that
the coupling between 2" dia coils separated by one foot of
air is 100%. If anyone can do that, I will admit I am wrong.
--
73, Cecil http://www.qsl.net/w5dxp