Topband: Modeling "Ground" and losses

[Jim Brown]

On Fri,2/27/2015 7:14 AM, Tom W8JI wrote:
> I don't think a description like that paints an accurate picture of 
> what actually goes on. 

I agree with Tom's analysis -- a good radial system SHIELDS the field 
from the earth, returning the field and the IN PLACE OF the lossy earth.

Studying N6LF's excellent work lit up the light bulb for me in several 
ways. First, by noting that current in a radial inductively couples to 
the lossy earth underneath it, which dissipates power. He also 
emphasized the importance of current in elevated radials dividing as 
equally as possible between them to minimize loss. The logic is simple 
-- since power is I squared R, uneven division causes a greater increase 
in the loss of a radial with more current than the decrease in the loss 
in the radial with less current.

That led me to this very simple, but very fundamental concept. Each time 
we double the number of radials, the current in each is divided by 2, 
but the power in each divides by four. This beautifully and simply 
corresponds to what we know about the power lost in radials.

Now, that simple analysis assumes a homogeneous earth, which we know is 
not real, so current division, and power lost in the earth, will vary as 
a result of that irregularity. But the fundamental concept remains the 
same. it also explains why we don't need as many radials to hit 
"diminishing returns" when the earth is less lossy.

73, Jim K9YC