> There seems to be some debate over multiconductor wire for grounding.
> As I see it, the only advantage of stranded cable is mechanical
> flexibility. I don't think "skin effect" (current flowing on the
> surface) has much to do with stranded wire, since the strands are all
> touching and are all in each other's magnetic fields. What is good is
At high frequencies, for the same outer diameter, stranded wire has
less effective surface area. That's because current pushes to the
outer edges of each stand, and the wire has an air gap between
strands that wastes space.
The finer the strands for a give wire size, the worse the wire
becomes at high frequencies as a general rule. (Lightning has a large
amount of high frequency energy.)
To see an example of this, look at loss specs for a given conductor
size coaxial cable that has solid smooth conductors, coarsely
stranded conductors, or fine thin multiple stands to make the cable
extra flexible.
This is why you NEVER see finely stranded wire in well designed
systems with high frequency high current applications like tank
circuits.
If the wire is woven into a braid, it really is a big problem.
Resistance and inductance can go way up, especially if the braid is
loose or dirty. That's the main reason coax gets so lossy when the
braid tarnishes from moisture. The braid from RG-8 cable handles
about the same 30 MHz current as number 16 or 18 solid wire. Better
if dry and tight, and worse if loose or tarnished.
73, Tom W8JI
W8JI@contesting.com
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