Stranded, layer-wound wire, even when strands are individually
insulated, behaves similar to solid wire of slightly smaller diameter.

The strands in true Litz are WOVEN such that every strand spends the
same length in inside and outside and intermediate layers of the
cable.

Current is then more uniformly distributed throughout the conductor's
cross-section.

The diameter of an individal strand should not be greater than about
about twice skin depth. Otherwise effectiveness decreases. Thus, at
high frequences where skin depth is very small, very fine wire must be
used.

There are practical and economic limits to the fineness of drawn
copper wire. There is little to be gained by using ordinary Litz
above 3 or 4 MHz. At high frequencies with small coils of few turns,
such as receiving coils, tank and loading coils, it is far more
economic to increase Q just by increasing the diameter of solid copper
wire. Litz is at its best from VLF to IF and MF.
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Reg.