ANTENTOP- 01- 2019, # 023

Spreading and Underground Antennas

Figure 13 shows underground Long Wave Transmitting Site. Antennas of the radio site are installed in the depth of 0.5-1 meter. Antennas may just lay in special kind of the ground or installed in center of plastic tubes in diameter near 1 foot. Feed lines from the antennas go through cable tunnel to Phasing and Matching Room. In the room there are installed matching devices for matching the antennas with transmitters and Phasing devices for creating desired radiation diagram.

Room with transmitters is located just below the room with phasing and matching devices. The operations control room and life-support systems are installed below or at the same level with the room where transmitters are installed. The Underground Long Wave Transmitting Site may get electricity through underground power electric cable or feed from diesel or nuclear power electric generator.

Some Experiments with Spreading Antenna

I tested a spreading antenna having 80 meter length that was lying on the ground.

Spreading antenna was made from old 75- Ohm coaxial cable with removed outer metal braid. Antenna had three counterpoises in 40, 20 and 10 meter length. Antenna fed through transformer 1 to 4 (75/300 Ohm). Monitoring Beverage antenna was installed at 20 meters apart of the spreading antenna. I used home- made transceiver with separate attenuator. Attenuator was savaged from an old RF Generator. Antennas were reconnected to the attenuator with help of RF Connectors. Figure 14 shows design of the two antennas and schematic of the test.

A-B test showed that on the 40, 20 and 10- meter Bands there was difference in receiving mode in 2- 6 dB, spreading antenna loose. In transmitting mode correspondents gave me 1- 2 balls on scale S for the Beverage antenna over the spreading antenna. On the 80 and 160 meter Bands the difference between spreading and Beverage antenna in receiving mode was near 6- 12 dB in favour of the Beverage antenna. In transmitting mode correspondents gave me 2- 3 balls on scale S in favour of the Beverage antenna.

Figure 13

Underground Long Wave Transmitting Site

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