LF and Litz wire

Andre Kesteloot akestelo@bellatlantic.net
Mon, 20 Apr 1998 07:38:20 -0400

LF enthusiasts,

Following a recent note on "rsgb_lf_group" by Martin Charman
G4FKK, I found the following information in my venerable
"RCA Radiotron Designer's Handbook" (RCA, NJ, 1941)  page

"Litz wire is most effective at frequencies between
one-third [i.e., 333 KHz] and 3 megacycles per second.
Outside of this range, comparable results are usually
possible with round wire of solid section, because at low
frequencies "skin effect" steadily disappears, while at high
frequencies it is large even in the fine strands forming the
Litz wire, and is augmented by the use of strands having
increased diameter." (That information was reprinted in
Langford-Smith, Wireless World Edition,1953, page 466).

As a footnote, Glenn KA0ESA and I have recently wound
several large (4" diameter, 2" high) one millihenry (1mH)
coils with 16 AWG stranded wire (as used for electrical
wiring) and compared them at 180 KHz with similar size,
commercially-manufactured coils made with litz wire.  At
that frequency (and therefore, presumably even more so at
136 KHz) there did not appear to be any advantage in using
the more expensive litz wire.

André Kesteloot N4ICK