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 antenna.
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 with sides of 240 cm Frame mounted on the ends of wooden slats cross section 20x20 mm. as the wire used in the antenna cord with a diameter of 2.5 mm.
To increase rigidity the squares are fastened together with four longitudinal rails cross section of 10X10 mm.
Active vibrator is fed at point a coaxial cable with wave resistance 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 "decimated"). In passive elements included in the circuits 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 radiation pattern of the antenna (the main lobe), filmed with the help of field indicator, referred to a distance of 100 m (10 lambda).
Fig. 2
During the operation of the antenna installed many neighbors (up to 200 km) and distant relations. Most correspondents estimated the strength of the signals S9 when the transmitter power of 10 watts.
Author: A. Terentyev (UB5GFI); Publication: www.cxem.net