Topband: Multiple Ground Systems

[Michael Rauh]

Gary, K9AY wrote:

"I prefer to think of a radial system as an approximation of a solid sheet 
rather than individual conductors."

Tom, W8JI wrote:

"Why does the current need to be in any particular direction 
Rick? That buss, assuming you have 50 radials or more, has a 
pretty low termination impedance for the small currents in 
the radial. While it may not be the shortest path possible 
to a distant area because of the angle, it is a pretty large 
path with a low impedance."

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I think now I better understand the "buss wire" connection.  Suppose there is
an EM field that wants to drive a tangential current in a dense radial field on
the ground.  A current could actually flow back to the junctions of the radials
and out again.  The parallel components of the current could cancel, leaving a
net current in the tangential direction.

The foregoing is naive, since it does not take into account inductive or
capacitive coupling between the radials.  I expect the coupling would enhance
the solid disk effect.

It would be fun to simulate this.  If only I had a copy of NEC4.

If the radial field is like a solid disk, it only makes sense to truncate the
overlapping portions.

ON4UN in his book often refers to a radial field as a screen.  That seemed
strange to me.  I thought a screen would need to be a mesh or a solid sheet. 
Again, if the radial field approximates a solid sheet, the screen idea makes
sense.

So,  if I have a dense radial field for my 160M vertical, perhaps I won't need
as many radials for my 80M four-square supported from the vertical?

Mike W8GT