[Lowfer] Coil question - Bowers

[Lyle Koehler]

When using coated magnet wire, the turns should be spaced two wire diameters
apart for best Q. Litz wire does not suffer as much from the proximity of
adjacent turns, so close spacing can be used. As far as I know, that is the
only advantage of Litz wire, and there is no point in using Litz with larger
wire spacings. When using plastic insulated building wire, the plastic
insulation thickness is just about right to provide the correct spacing
between adjacent conductors. And as others have pointed out, only those few
LowFER installations with extremely low ground losses will notice a
significant benefit from a coil Q of more than a few hundred, which is
relatively easy to obtain.

The optimum coil diameter to length ratio of approximately 2.5:1 is for a
coil with a turns spacing of two wire diameters. This is the form factor
that gives the maximum inductance for a given total wire length on a
single-layer solenoidal coil. But the curve is pretty flat, and other form
factors such as 1:1 or 1:2 will work almost as well.

Lyle, K0LR