For communication in the range of 28 - 29.7 MHz radio UB5GFI an antenna "triple square" with vertical polarization (see Fig. 1). Vertical polarization is used to achieve a strong connection straight beam, as most fans are used in this range whip antennas.
Fig.1
The antenna consists of an active vibrator with a side of a square 259 cm reflector with a side of 269 cm and Director of 240 cm with a side Frame mounted on the ends of wooden slats section 20x20 mm. as the wire used antenna cord with a diameter of 2.5 mm.
To increase the rigidity of the structure squares held together by four longitudinal rails cross section 10 X 10 mm.
Active vibrator is fed at point a coaxial cable with a characteristic impedance of 75 Ohm. The metal core is connected to the lower cover to the upper wire frame (found that when such a connection diagram of the antenna less "mows"). In passive elements included plumes of symmetrical two-wire line with the distance between the wires 10 and a length of 50 cm Cables attached to the horizontal rails and are located inside the squares.
In Fig. 2 shows the experimental transmission beam (main lobe), taken with the indicator field is related to the distance of 100 m (10 lambda).
Fig.2
During the operation of the antenna installed many neighbors (up to 200 km) and long-haul communication. Most correspondents were estimated force signal S9 when the transmitter power of 10 watts.
Author: A. Terentyev (UB5GFI), Dnipropetrovsk; Publication: N. Bolshakov, rf.atnn.ru