Hi Mike,

Have a look at :

http://www.wireless.org.uk/dk5pt-f.htm

It shows a very small loading coil (using a pot core) made by DK5PT.

73, Rik  ON7YD

Just to clarify, the problem I am trying to fix is to get the lowest loss

coil on top of the mast with minimum visual impact. I am already doing this with a lot of wire on a drain pipe, but at the expense of resistive loss.

Litz coil  (with thicker wire) is the same physical size, much lower loss

half the inductance.