ANTENTOP- 01- 2019, # 023

Spreading and Underground Antennas

The underground vertical antenna shown in Figure 8 was used at German Mountain Underground Radio Site during WWII. The site was operated in the Carpathians Mountains. Mountain Underground radio sites are very rare because it is difficult to find suitable place for the mountain antenna.

Cave Antennas

A kind of underground antennas is the Rhomb Underground Loaded Antenna. Before WWII, Rhomb Underground Loaded Antennas were tested in Russia in the Crimea and Georgian caves. Antenna wire may be placed underground as in vertical either in horizontal position depends on the cave.

Figure 9 shows the Rhomb Vertical Underground Loaded Antenna.

The part of the antenna AB is placed immediately on the surface of the ground or at a small depth under the surface. The parts AC, BD, CD are placed in a hole either artificial or natural. The rhombic underground vertical antenna, as well as the above ground version has radiation directed toward the termination load. By switching the load from point B to point A, and accordingly switching feed point from point C to point D, the antenna directional radiation diagram could be changed to 180 degree.

Figure 9

Rhomb Vertical Underground Loaded Antenna

Figure 10

Antenna Wire for Underground Antenna

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