> FWIW: I tested a 1000 foot run of open wire line
> made with STRANDED aluminum 4 AWG THHN wire. It
> was very low loss, a few tenths of a dB on 160
> up to about a dB on 10 meters. I would say that
> the stranding didn't cause much harm, based
> on these results. Just an anecdote.
In amplifier tank circuits at HF carrying high current, braid from RG-
8/U will overheat and melt while #14 tinned buss wire will barely get
warm. If you simply tin the length of braid making it one conductor
(of mostly lead) the problem disappears. That's a remarkable
difference.
The same thing happens in RF relays. Woven armature leads
overheat and fail at much less current than stranded leads, which
are not as good as thin flat foil leads.
Stranded wire is much less of a problem that woven or braided wire
(the more rapid the weave the worse the problem), the effect in
stranded wire is of one of losing surface area because of both
proximity and skin effects. When I get some time while doing some
high-current work, I'll measure the effect and quantify it for various
wire types.
Lightning is another issue entirely. Braided conductors (and
stranded conductors) are a very real problem.
All in all, it is a good idea to not go out of our way to use stranded
or braided wire. It is never better for anything except when being
repeatedly flexed. And it is certainly no good when exposed to
weather or high current/lightning!
73, Tom W8JI
W8JI@contesting.com
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