Antenna Dipole. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / HF antennas
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Radio amateur V.Voliy (UA10DL) spoke about the design of the antenna brought to the attention of the reader on the air about 15-6 years ago, for which the author is very grateful to him. The antenna is still working and due to the absence of the need for switching and adjustment when switching from range to range, it is often used as a surveillance or backup antenna. Measured SWR values at frequencies of 1,9 MHz - 1,9; 3,6MHz-1,3; 7,05MHz-1,2; 14,1MHz-1,4; 21,2MHz-1,7; 28,6-1,6.
Structurally, the antenna is an ordinary dipole (see Fig.) with a beam length of 20,5 m, which is powered by a coaxial cable with a wave impedance of 50 or 75 ohms.
(click to enlarge)
As a matching device, a two-wire line with a wave impedance of 300 (CATV cable) 17,7 m long and a balancing broadband transformer 1: 4 (T) is used.
The transformer is wound on a ferrite ring with a permeability of 30-50 HF with an outer diameter of 24 - 32 mm, depending on the power supplied to the antenna (a ring with a core cross section of 1 square centimeter is capable of transmitting about 500 W without damage). If one ring is not enough, then take two, three rings, folded together. Before winding, the ring (rings) is pre-wrapped with a heat-resistant insulating tape, for example, fluoroplastic, because. at maximum power, the ring can be heated up to 70 °C. Both windings of the transformer contain 9 ... 10 turns wound simultaneously by two pieces of PEV 0,8 ... 1,0 wire folded together or a stranded wire similar in cross section in fluoroplastic insulation (not afraid of heating). The windings are placed evenly around the circumference of the ring, and the desoldering is performed according to the diagram in the figure, where the dots mark the beginnings of the corresponding windings. The transformer is protected from moisture by wrapping it with insulating material and varnishing it.
The points of connection of the transformer to the two-wire line are located at a distance of 5,9 m from the junction of the line with the antenna canvas. The antenna fabric is made of 02 mm galvanized wire, and only because of this, the described multi-band dipole stood for such a long time in the difficult environmental conditions of Donbass.
Literature
- Radio hobby 1/2001
Publication: N. Bolshakov, rf.atnn.ru
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