ANTENTOP- 01- 2019, # 023

Spreading and Underground Antennas

Underground radio sites that used the Vertical Rhombic Terminated Antenna are restricted to area in which the terrain has high resistance and a small dielectric constant. Therefore it has a low absorption of Radio Waves.

For antenna wire of these antennas, a wire with a diameter of 1 mm in plastic insulation with a diameter of 10 mm was used. It is like a thick coaxial cable with the outer conductive braid removed. However the cable has strong plastic outer covering. Figure 10 shows the antenna wire.

Underground Radio Sites for Long Wave

Underground radio sites for Long Wave and Super Long-Wave are more common the Short Wave Underground Radio Site. The sites are used for navigation and for emergency radio communications. Sometimes at a short distance from a Long Wave Radio Site it is placed a Short Wave Radio Site. The antennas at the Long Wave Radio Site usually are not used for short wave communications however in rare occasions there have been double applications.

The length of effective spreading (or underground) antenna on Super Long band as usual is in limits 150 -250 meters. Because due losses in the ground it is hard to improve efficiency of antenna just by length. To improve the antenna efficiency on the Underground Radio Communication Site of Super Long Wave there are used to a quasiresonance antennas. Figure 11 shows design of the spreading antenna for Super Long range.

The antenna consists of two bent elements 1 and 4 which with the help of the matching devices 2 and 3 are tuned to resonance. The antenna at top view has shape of a boomerang. Therefore such antennas in the USSR have the nick name Boomerang.

 There are underground Long Wave sites where there are used several antennas, as usual 4 or 6. These antennas feed through phasing devices that may create desired directional radiation pattern. Figure 12 shows the top view of such spreading antenna system. This antenna system has nick name Spider, because it looks like a spider from the top view.

Figure 12

Top View of Spider Spreading Antenna System

Figure 11

Design of Spreading Antenna for Super Long Range

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