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Re: [TowerTalk] Copper Vs AL Was UV and WX deterioration of THHN insulat

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Subject: Re: [TowerTalk] Copper Vs AL Was UV and WX deterioration of THHN insulation, and effects
From: jimlux <jimlux@earthlink.net>
Date: Fri, 30 Dec 2016 07:24:32 -0800
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
On 12/29/16 10:22 PM, Roger (K8RI) on TT wrote:
How does the resistivity of the Copper Chloride (What you get with
Chlorine and moisture  on the surface of the Copper wire) on the surface
of the Copper wire compare to the resistivity of Aluminum wire?

I looked up conductivity of various copper compounds - copper oxides, copper chloride, etc.

They're all really high resistivity (not as high as Alumina), but more importantly, some of them do dissolve in water (to some extent), which changes their resistivity at DC (and RF, but it's a ion mobility thing), so you might see a tiny difference between dry and wet conditions.

High, here, means resistivities in the 1000s of ohm-cm bucket, which is where wet wood is Compare to copper at 1.68 micro ohm-cm - that's 9 orders of magnitude different.
Sea water is 20 ohm-cm
carbon is .005

In all cases, for any plausible thickness (up to the diameter of the wire), no significant current flows in the corroded layer..



 I ask
as I've seen number of posts on newsgroups where Al wire was being used
for radials.

Actually, aluminum wire would be a good choice for above ground antennas - it might be cheaper than copper, even if you buy larger gauge to make the resistance the same as copper. You'd need to go up in diameter (not area) by a factor of 1.67 - that's about 4.5 AWG gauges.. (double diameter is 6 gauges)



Roger (K8RI)

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