131 shows that the closer a horizontal antenna to the
ground the more horizontal component at Electro- Magnetic Radiation
of the antenna. However the closer an antenna is to the ground
the less efficiency of the antenna.
Efficiency is lowered because of the losses
in the ground and in the antenna wire. The losses rise dramatically
with increasing of the working frequency of the antenna.
Figure 145 shows experimental
data of the (antenna) gain by the ground wave for TWA of the 150
meter length of wire hanged at 2.8-meteres above the ground and
Grounded Antenna - Insulated Wire in 150- meter length sitting
on the ground. If the Grounded Antenna would be made from a naked
wire the antenna dramatically decreased (compare to grounded antenna
from the Figure 145).
Installation of the ground antenna is much easer the
TWA. However, a ground antenna is much easer to damage compare
to TWA. It is happened by moving vehicles. TWA is usually hang
up at a height 2.8- 3 meter to avoid the damage by the vehicles.
Sometimes for grounded antennas is used a usual horizontal dipole antenna
located straight over the ground.