[TenTec] Vertical radial question

[Lee A Crocker]

I read Rudy's article.  I don't see a disconnect.  The
absolute values are different but the morphology of
the curve is similar.  Further if you extend the
radials out lets say from 60 1/4 wave to 120 1/2 wave
to 240 full wave the field strength will continue to
grow as you are now effecting the near far field,
which starts somewhere around 1/3 of a wavelength.
N6RK did some work on this with very long radials
pointed toward Europe and found he could improve his
signal to Europe  with very long radials.  If you
however collapse that 240 1 lambda amount of wire into
960 1/4 wave radials your field strength will plummet.
 Rudy says this basically in his article when he
states he would expect .3dB gain by adding another 1.5
miles of wire.

The point being for a given short radial length (let's
say .1 lambda) you will reach the point of diminishing
return faster.  In other words if you put out 64 .1
lambda radials you would probably not see any more
increase in field strength than if you put out 32 or
maybe even 16.  

I ran an experiment, that I later saw a similar
experiment on W8JI's site when I was playing with a
radial field.  I had a ground rod planted next to the
antenna and I had a RX out far away measuring field
strength, linked to a laptop which I was then able to
watch the S meter on another laptop near the antenna
base.  When I added some radials the field strength
went up.  When I added the ground rod the field
strength went down.  Added more radials strength up,
ground rod added, strength down but down less. 
Eventually I had enough radials that the ground rod
made little difference.  I think this is the point of
diminishing return.  

What I think is going on is the radials collect the
current induced in the ground by the monopole and
provide a relative low impedance path to get back to
the shield of the coax.  When I added the ground rod
it shunted some return current to ground that is to
say there was as if s potential difference between one
end of the ground rod and the other existed (for a
theoretical illustration, I don't think this is
physically what is happening) and some current was
shunted into the ground rod and less current
effectively reached the coax shield.  As more and more
wire is added the potential difference gets smaller
and smaller and more and more current gets returned to
the coax shield until basically the radial field is
maximally coupled into the ground, and all the ground
current available to be abstracted from the ground is
effectively being returned to the shield of the coax,
from the given volume of ground that the radial field
is coupling into.  If you involve a greater volume of
ground you can realize more current and hence a better
efficiency.  It would be interesting if Rudy could add
the ground on -ground off piece of data when he
re-dose his experiment.

It made me think of a radial field in a whole new
light.  It's more about effective coupling into a
volume of ground and less about absolute numbers and
such.  If there is a better explanation to what I
observed I'm interested in hearing it.

73  W9OY  


 
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