Topband: Wire Guage VS Resistance

[Tom Rauch]

Hi Thomas,

I know it was a lot of work, but you quoted dc resistance.

DC resistance and RF resistance are entirely different. Tables for 
dc or very low frequency ac do not reflect the resistance at radio 
frequencies. I'd hate for people to think the change in RF 
resistance (what I was talking about) is as small as the change at 
dc (which you listed)!!!!

In stranded wire, high frequency RF current only flows on the 
outermost edge of each stand...it doesn't even flow on the inside 
edge of outer stands (let alone the core stands)...so you can 
imagine how thin the conductors "look" for RF (and much of the 
energy in lightning).   

Braided wire is even worse than stranded, because the current has 
to cross over between thousands of tiny pressure connections as it 
goes along a long length of braiding. The current always is forced 
on the outside layer. When an outer lay turns in towards the 
center, current tries to find a path back to the outside through 
pressure connections at every single weave! 

If the current is low, you won't notice any difference because even 
multiplying loss several times in that case means nothing. In other 
applications, the change can be significant. Like lightning 
protection applications, or in short antennas carrying high currents. 
It is also bad in tank circuits or RF inductors.

73, Tom W8JI
W8JI@contesting.com 



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