Jim, it is my understanding that unless the radials provide a perfect
shield over the ground, some of the return current will flow through the
radials and the rest through the ground. More radials provide more
shielding and, consequently, carry a greater fraction of the current
relative to the ground. Perfect shielding would mean the radials carry
all the current. Presumably, Brown's 120 radials come to close to this
ideal.
If a perfect ground were available (zero resistance), one wouldn't need
any radials at all and just a connection to ground. In the real world,
one has neither perfect ground nor a perfect shield, so the return
current is divided between the two parallel paths. If one then
increases the conductivity of the ground through deliberate salting (or
degradation of a chicken wire screen in this case) and the number of
radials remains constant, then the overall return path resistance is
lowered and the efficiency of the vertical is increased because of the
reduced IR losses. Maybe the degraded chicken wire wouldn't make up for
the original screen, but the net return resistance would be less than if
the the radials were used by themselves over the same soil in an
"unsalted" condition. (Note that that these radials are separate from
the chicken wire screen.)
If this is not an accurate description of what's happening, then I'm
open to being corrected.
Thanks for your input.
73, Joe
K2XX
Jim Brown wrote:
> On Fri, 12 Jun 2009 17:06:29 -0400, Joe Giacobello wrote:
>
>
>> OTOH, wouldn't the remnants of the wire and its degradation products
>> enhance the conductivity of the soil surrounding the antenna so that
>> the remaining radials are now more effective?
>>
>
> NO! Go back to the ARRL Antenna Book and re-study the chapter on "The
> Effect of Ground." Radials have NOTHING to do with the earth. Radials
> REPLACE the earth in the antenna circuit by providing a much lower
> resistance path than earth for the current and fields produced by
> antenna current.
>
> 73,
>
> Jim Brown K9YC
>
>
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