ANTENTOP- 02- 2010, # 014

Grounded and Underground Antennas

Trench Antenna installed into closed trench is shown at the Figure 149. 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 frequencies increase.

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.

Figure 149 Trench Antenna installed in the closed trench

73! I. G. 

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