Topband: What wire to use for 'wire' TX antenna

Tom Rauch
Thu, 26 Jul 2001 08:51:14 -0400

> occurred at 800W)!  With the various online antenna
> wire & cable companies advertising "flex-weave" and
> other elaborate wires for 'wire' antennas, what seems
> to work well?  Seems like "freedom from kinks" and
> "rugged" might not go together.  I suppose I need
> better than 14 gauge; that's what melted!  I still
> can't believe I had a current node that high - on a
> physically short antenna?

Woven or braided conductors have a lot more resistance per unit 
length than smooth surface conductors. Clean, shiny braid that is 
compressed (like the braid inside coax, compressed by the jacket) 
has about four times the loss resistance of a smooth conductor the 
same size and material. That's why most low loss cables have a 
smooth metal foil or solid tubing for a shield, and use solid center 

Coax braid, if you look at it, is a gradual weave with strands laying 
side by side and yet it still increases loss.

If you remove pressure from the weave, RG-8/U size braiding has 
about the same resistance per foot as #14 or 16 solid copper wire 
on 30 MHz. 

When that braid is exposed to weather or moisture and tarnishes, 
the RF resistance really increases. As a matter of fact that is 
almost the entire reason wet coax gets so lossy...and why it 
doesn't recover even after it drys out inside!

The denser the weave, the poorer the conductor at RF and the 
quicker corrosion will make the resistance increase even more. 

How much this matters depends on how much current flows in the 
conductor. It might not matter in some antennas and in others it 
could easily be a show-stopper. It certainly is bad news for 
lightning protection.

73, Tom W8JI 

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