[TowerTalk] 80M antenna wire size

[K9MA]

Stranded copperweld used for antennas and feedlines can corrode due to 
the strands rubbing together and wearing through the copper, exposing 
the steel.

73,

Scott K9MA


On 1/3/2020 14:31, Shawn Donley wrote:
> Some good reading on this topic can be found at https://rudys.typepad.com/files/qex-nov-dec-2k-antenna-wire-conductors.pdf
>
> I discovered Rudy's paper after searching for information on the effect of conductor oxidation (stranded antenna wire).   It's always bothered me that with stranded wire (hard drawn copper or copperweld) the strands are somewhat "insulated" from one another by surface oxidation.  If skin effect forces currents to the outside of the net diameter of the stranded wire, what effect does the surface oxidation have on losses?   I suppose if the radiation resistance of the antenna is high, the effect on efficiency is small.  But not so for antennas with a low radiation resistance.
>
> Rudy's paper is the only source I've found that attempted measurements (indirectly via Q of coils wound with oxidized wire).
>
> Doing some antenna work this past weekend (unusual warm weather) I also discovered that some ladder line I have shows significant oxidation on the conductors, many feet away (50+) from the end of the ladder line.  It's stranded #14 copperweld ladder line.  No obvious cracks in the insulation that would let water in.  Perhaps the corrosion is due to interaction with the insulation material itself.  I separated the strands on a cut end and found them all to be visually blacked rather than the expected shiny copper.  After cleaning up the ends of the strands with #400 paper, I measured as much as 2 Ohms resistance between strands with my DVM (that's strand to strand on the same end of an open feedline).  No idea what the losses may be at RF.
>
> N3AE
>
>
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-- 
Scott  K9MA

k9ma at sdellington.us