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Grounded and Underground Antennas

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ANTENTOP- 02- 2010, # 014

Grounded and Underground Antennas

 

Figure 145 Experimental data of the (antenna) gain Vs frequency by the ground wave:

 

1. Travelled Wave Antenna  - 150 meter length of wire  hanged at 2.8-meteres above the ground

2.   Grounded (sitting on the ground) Insulated Wire in 150- meter length

 

Underground antennas are more long life compare to TWA and Ground Antennas. Underground antennas can work because horizontal component of the EMF (Electromagnetic Field) can penetrate into the ground (Figure 131). So, as a rule a horizontal wires used for underground antennas.

 

Efficiency of the underground antennas is depended onto parameters of the soil. Antennas placed into wet soil have gain less compare to antennas placed into dry soil.

 

The decreasing of the antenna gain of the underground antenna in the wet soil can be explained by increasing of the attenuation of the radio- wave in the antenna wire (but not the attenuation of the radio- wave in the wet ground).

 

To increase the gain of the underground antenna it needs that a low- losses dielectric would be placed around the antenna wire and the soil. To this effect the wire of the underground antenna concludes in a rather thick plastic shield (Cable Underground Antenna)

 

 (Note from I.G.:I had several pieces of the antenna wire from the underground antennas. It was copper wire inside the round (16-mm OD) white thick plastic shield. A strong black plastic (thickness near 1-mm) was above the white plastic shield) or installed the antenna in the underground cavities or trench (Trench Antenna).

 

Often an usual coaxial cable is used for installing the Cable Underground Antenna. Figure 146 shows real design of the Cable Underground Antenna.

 

The antenna is made from a length of 15-meters of a Russian coaxial cable RK-3 (or RK-6). Table 1 shows data for some old- age Russian Coaxial Cables. Copper braid is removed at the length of 10 meters (part 1 of the antenna). Antenna is dug in a trench onto depth of 0.2- 0.5- meters.

 

Antenna is located to the needed direction. Part 2 of the antenna is the feeder. The feeder is going to bunker 3 where a transmitter is installed. Part 4 shows terminal for connection with a transmitter.

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