[TowerTalk] 80M antenna wire size

[Grant Saviers]

Stranded wire has plenty of spaces for water to capillary wick the 
length of the wire.  Once I tried to make a pressure tight connection 
from insulated stranded wire -  it leaked like a sieve.

Way back, I asked my boatyard mechanic why he was soldering crimped 
terminals, his answer was "in three years you will thank me".  If there 
are chloride contaminants in the air, the corrosion process is greatly 
accelerated. (see 
https://pomametals.com/wp-content/uploads/2018/04/salt-air-inland-coastal-map.jpg) 
  I have observed that some insulation, particularly older rubber 
insulated wire, has contaminants that accelerate corrosion, yielding the 
black oxide, a real PITA to clean for soldering.

Grant KZ1W


On 1/3/2020 20:31, 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
> 
> 
> _______________________________________________
> 
> 
> 
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>