[TowerTalk] RF Ground

[Tom Rauch]

> thinking of making a RF ground/radial on the roof. I have been given
> access to a "free" supply of 1/2" copper tube, ex water heating. I
> have read that it is better to have a flat section rather than a round
> section for the ground/radials. I am thinking of "flattening" the tube
> which would give approx 3/4" wide copper strip.

Hi George,

I think "Ask the Doctor", in QST, gave an incorrect answer to the 
very same question you are asking. I *think* they said if you 
flattened the conductor, the resistance would decrease, but I only 
scanned it quickly and can't recall the issue to look back at it. 

The lowest loss resistance would come from a round conductor. If 
you flatten it, current bunches at the edges and the losses go up. 
There is less-even current distribution in a flat conductor with the 
same surface area as a round conductor. Of course if you pounded 
it into very wide thin strips, you could increase the total surface 
area...but that would take some real pounding. Better to pound 
brass instead.

For what you are doing, none of this makes any difference. You 
could use #18 wire, or something as fat as your thumb, and things 
would hardly change. That's because current in each radial is 
small, and the radials are in "parallel" at the common point. The 
number of radials is much more important than how thick they are.
73, Tom W8JI
W8JI@contesting.com 

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