AdvancedA-007-007-003
The plane from which ground reflections can be considered to take place, or the effective ground plane for an antenna is:
B
Answer
Interference, EMC, and safety
Type
A
at ground level exactly
B
several centimeters to as much as 2 meters below ground, depending upon soil conditions
C
as much as a meter above ground
D
as much as 6 cm below ground depending upon soil conditions
Answer Notes
Ground reflections for radio waves do not happen exactly on the physical surface of the earth. Instead, the effective ground plane is the electrical boundary where reflections actually occur.
Because soil has varying conductivity and dielectric properties, RF energy penetrates the earth before being reflected. Depending on soil moisture, mineral content, and the specific frequency being used, this effective plane can exist anywhere from a few centimeters to as much as 2 meters below the actual surface.
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Most simple horizontally polarized antennas do not exhibit significant directivity unless they are:
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Why is a ground-mounted vertical quarter-wave antenna in reasonably open surroundings better for long distance contacts than a half-wave dipole at a quarter wavelength above ground?