On 12/10/2020 11:14 PM, Raymond Benny wrote:
With said, I believe my ground absorption is very high so I feel the higher
numbers of radials helps greatly with my vertical efficiency and radiation.
Hi Ray,
The soil affects us in two important ways. First, poor soil burns
transmitter power underneath the antenna and it's near field. We use
radials to shield the soil from the field, and to supply a low impedance
path for return current. Magnetic fields produced around each radial by
virtue of current flow couples loss in the earth into the radials in the
form of series resistance. Loss in each radial is 1 squared R; each time
we double the number of radials the current in each is divided by two,
so the power coupled to the earth by each divides by four. So the more
radials, the less power is coupled to the earth. THAT'S why more is
better. The result of all this is that loss in the soil under the
antenna reduces the total strength of our signal by that amount.
The second effect of soil is in the far field, where we field radiate
hits the earth and is reflected by it to form the vertical pattern. The
better the conductivity THERE, the our pattern will be both stronger and
at a lower angle. An antenna with its base just above sea water is the
extreme example of this -- the reflection is extremely strong, and it is
at a VERY low angle.
We can help the first of these two effects with a good radial system,
but the only thing we can do about the second (the far field
reflection), is to move where there is better soil. Most of us live
where we do because we like living there for reasons other than radio.
And that includes me and my XYL.
73, Jim K9YC
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