Antenna Triple square. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / VHF antennas
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For communication in the range of 28-29,7 MHz, the UB5GFI radio station uses a Triple Square antenna with vertical polarization (see Fig. 1). Vertical polarization is used to achieve reliable direct beam communication, since most amateurs use whip antennas in this range.
Fig. 1
The antenna consists of an active vibrator with a square side of 259 cm, a reflector with a side of 269 cm and a director with a side of 240 cm. The frames are fixed at the ends of wooden slats with a section of 20x20 mm. An antenna cord with a diameter of 2,5 mm was used as a wire.
To increase the rigidity of the structure, the squares are fastened together by four longitudinal rails with a section of 10x10 mm.
The active vibrator is powered at point A by a coaxial cable with a characteristic impedance of 75 ohms. The central core is connected to the lower wire, the braid is connected to the upper wire of the frame (it has been established that with this connection the antenna diagram is less “skewed”). The passive elements include loops from a symmetrical two-wire line with a distance between wires of 10 and a length of 50 cm. The loops are attached to horizontal slats and located inside squares.
On fig. 2 shows the experimental antenna pattern (main lobe) taken with a field indicator spaced at 100 m (10 lambda).
Fig. 2
During the operation of the antenna, many short-range (up to 200 km) and long-distance communications have been installed. Most correspondents estimated the strength of the S9 signals with a transmitter power of only 10 watts.
Author: A. Terentyev (UB5GFI); Publication: cxem.net
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