[Antennas] Need a bit of wire advice

[George, W5YR]

Interesting . . .

Seems to me, and I think that Mother Nature concurs, that the layer of bad
crud would be no different than a layer of insulation (good crud) on the
wire. The current flow will always be on the surface of the lower
resistance conducting path which will be the uncorroded copper beneath the
crud. 

I suspect that a negligible amount of r-f current would try to make its way
through the poorly conducting copper oxide. So, its higher resistance is
immaterial. I seriously doubt that any measurable difference in
driving-point impedance can be seen between a shiny new copper antenna when
it is first erected and a few weeks or months later when it has built up
its layer of crud.

Connections, IF made through the crud, would have higher resistance, of
course. But all r-f connections to the antenna will sensibly be made to
clean copper with solder so that there is intimate contact between the
feeder copper and the antenna copper, even though both may acquire a layer
of crud over time.

As to corrosion, many copper wires - antennas and otherwise - have managed
to stay up for years without succumbing to deterioration from copper oxide.
My limited understanding is that the oxide layer actually does insulate the
wire from further corrosion by other agents and acts as a protective layer.
And, that once the oxide layer is formed, its chemical reaction with the
copper stops and no further crud develops.

Don, I guess we just don't agree on this one . . .

72/73/oo, George W5YR - the Yellow Rose of Texas         
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe   
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771
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Don Havlicek wrote:
> 
> The 'built-up crud' is oxidation.
> Copper Oxide and/or copper sulfate [IF sulfur is absorbed from the
> atmosphere], are both corrosive and have higher resistance to electron
> flow .. at DC or RF.  Connections with 'crud' will be higher resistance
> .. affecting the impedance of the antenna.
> Don
> N8DE