Trench Antenna installed into closed trench is shown
at the Figure
DD of the antenna is practically similar to DD shown on the Figure 133 B.
However the back lobe has trend to decrease when the operation
Keep in mind that efficiency of the Trench Antenna
may be significantly decreased when the radiation part of the
antenna is touched to the wet ground. Keep the radiation part
at least 10- 15-cm out of trench wall. To keep good performance
of the Trench Antenna do not place the radiation part more the
50 – cm from the ground level. Small masts with end insulator
(or dry sticks) may be used in the design of the Trench Antenna
to hold the radiation wire.
Counterpoises placed toward to radiation part of the
antenna. Usually counterpoises dug on to small depth into the
ground. At the band 1- 6 MHz the antenna (Figure 149) is almost equal to vertical antenna
in 4- meters height.
In conclusion it is necessary to say that Underground
and Trench Antennas are less efficiency in radiation of the ground
and sky wave compare to antennas installed above the ground. So
the Underground and Trench Antennas cannot provide far communication.
However the good masking and survivability of the Underground
and Trench Antennas allow use it in the military application.