[ARC5] HF Demonstrations

[Tom Lee]

At RF, current does not flow uniformly across the cross-section of a 
wire (the current flow of an isolated wire will be primarily on the 
surface) so resistive losses are higher than at DC (it's called the 
"skin effect"). If instead of a single wire you use a bunch of 
individually insulated parallel strands and twist the bundle, the 
current distribution becomes more favorable. That's litz wire ("litz" 
comes from the German for "woven").

Of course, the insulation takes up space that reduces the useful 
cross-section, which tends to increase resistance, so litz wire has a 
tradeoff that reduces its effectiveness toward the top of the AM BCB. 
Above about 2MHz or so, there's a transition from "not helping much" to 
"worse than a solid wire".

-- Cheers
Tom

-- 
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu