Hi Chuck!
The 6 dB gain from reflection from perfectly conducting soil is based
on simple preservation of energy.
Because of ground reflection, an isotropic antenna can only illuminate
half of free space (the reflecting surface blocks all radiation below the
horizon. This "blockage" is responsible for the first 3 dB of
ground gain.
However, the ground reflection also produces an interference pattern of
peaks and nulls in the radiation pattern. The energy from the nulls adds
3 dB of additional ground gain to the peaks in the radiation pattern of an
antenna over perfectly conducting ground.
Hope this clarifies things for u!
73
Frank
W3LPL
donovanf@sgate.com
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