Hello Pat,
The fresnel zone is the earth in the direction of transmission and reception.
The waves hit the earth and reflect at the inverse angle and combine giving a
6db maximum gain. The 6db is not exact due to losses but is much nearer 6db
that would be expected. At low angles of radiation, the effiency is
particularly good. The frenel zone usually encompasses many acres of land. If
this land is in a Box Canyon, its time to call a realtor.
Puesdo-Brewster angle losses are the reason vertical antennas are not able to
take advantage of fresnal zone enhancement. Reflections at very low angles are
not of the correct phase to enhance the wave.
The ARRL handbook covers this in the chapter entitled "Effects of the Earth"
73 Don W7DD
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