On Sun, 15 Mar 2009 12:39:55 -0600, DAVID CUTHBERT wrote:
>For example, perhaps rather than 100 watts and an extensive radial
>system I can run 1500 W to a ground rod system
That's about right -- not quite 12dB of loss for not having radials.
And if you had the radials, you could overcome a 12dB higher noise
level (or path loss) at the other guy's QTH.
>This might shed more light on this murky thing we call 'RF GND."
It's not at all murky if you study what N6LF has written in the ARRL
Antenna Book. The current in the earth (or the radials) is the
result of the antenna's fields finding it. In other words, the
radials complete the path for the antenna.
The best way to understand the earth's contribution is to realize
that the earth under a vertical antenna is burning transmitter power
(as your example suggests), while the earth at greater distance from
the antenna REFLECTS the transmitted wave. An antenna's vertical
pattern is the result of the addition (algebraically) of the direct
wave and the reflected wave. The pattern is "big" at vertical angles
where they add more nearly in phase, and small when they are more
nearly 180 degrees out of phase.
73,
Jim K9YC
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