ANTENTOP- 01- 2019, # 023

Spreading and Underground Antennas

Antenna wire is a copper (at some references the wire made from a special brass) cord in thick strong plastic insulation. The length of this wire is 60 meter.The wire is strengthening with a steel core inside the copper cord. The antenna wire is going through plastic triangular insulators, which help keep it is isolated from the earth. The insulators placed at distance near 1.5 meter apart each other. The plastic triangles may be inserted into the ground by one end therefore they were made from a strong plastic.

The two-wire ladder line in strong plastic insulation is connected to the antenna wire and the counterpoise. The two wire line connected the antenna and counterpoise is going to transmitter. The length of this two wire line is 5 meter. The length of the counterpoise is 15 meter. Termination Load has 300 Ohm value. Load is protected from mechanical damage, water and atmospheric influences. The length of the counterpoise after termination load is 15 meter. Both counterpoises made from the same antenna wire. Counterpoises were connected to steel pins in 70 cm long, which were hammered into the ground. The antenna was operated in the frequency range from 1 to 50 MHz. The maximum power going into the antenna was depend on dissipative power of the termination load. There was antenna option for 5 kW RF power ever.

In the internet I found description one more very interesting Russian Spreading Antenna. The antenna is mentioned to be produced in 70s. Antenna is named SA- 60-2M-PK (CA-60-2M-PK, in Russian letter). Figure 5 shows design of the antenna.

The outer sheath of the antenna is made of from strong foam insulating material that could be floated on the surface of both fresh and salt water. The diameter of the plastic body is 16 cm. The surface of the plastic was special and it repelled water and dirt. The plastic insulation of this antenna was non-flammable. According to technical parameters, this antenna can withstand being run over by a tank weighting up to 100 tons. It does not fail even with close explosions of a nuclear bomb and direct hits by shells or mines.

Antenna wire in part B made from copper cord in diameter of 4 mm. The counterpoise of part A is made from a wire, similar to the antenna wire. Counterpoise of part C is made from a cord having a pure dc resistance of 100 ohms at its ends. This counterpoise is artificial termination load of the antenna. It allows the use to the antenna without grounding pins and on any type of the ground- sand, stone, permanent ice, etc. Special design of the artificial termination load allows match the antenna in the wide frequencies range.

A two-wire line by length of 5 meters is connected to the antenna. According to technical parameters the antenna works in frequencies range of 1-50 MHz and could stand up to 5 kW RF Power. This antenna is still workable if it is buried at a small depth in the ground.

Design of Underground Short Wave Radio Site

The underground radio sites were arranged for navigation and for emergency purposes, as a commander radio site. The commander underground communication sites were designed for operation on LW, MW and HF ranges. Figure 6 shows design of a commander communication site for operation on HF bands.

The underground radio site consists of Equipment Room (1) located at depth of 15-30 meters underground. The room contained transmitting/ receiving equipment and place for personnel. The transmitting/ receiving equipment is connected by feeders (2) to the matching devices (3). Matching devices is placed at depth of 2-4 meters from the surface of the ground. The 4- 8 aperiodic loaded antennas (4) are connected to matching devices. The length of each of the antenna may be in range of 20 to 50 meter.

Figure 5

Spreading Antenna SA- 60/15 60-2M-PK

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