Antenna 5/8l at 27 MHz. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / HF antennas
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Antenna "ORION-5/8" produced in series is designed to work with a base radio station of the civilian range of 27 MHz. The main advantage of this antenna is that the main lobe of the radiation pattern in the vertical plane has a minimum angle (Fig. 1).
Ris.1
This means that most of the energy emitted by the transmitter is concentrated close to the earth's surface, which allows low power transmitters to be used with maximum efficiency. The length of the vibrator is 5/8 of the wavelength. Antenna resonance is achieved by turning on an extension coil, which contains 8 turns with a diameter of 40 mm, the length of the winding is about 100 mm. The coil is wound with a wire or a busbar with a cross section of at least 2 mm2.
Specifications:
Gain - 6 dB;
Input impedance - 50 Ohm;
SWR - no more than 1,5;
Bandwidth - 26,5 - 28,2 MHz;
Directional pattern - in the horizontal plane - circular; - in the vertical plane - see Fig.1.;
Wind load - 25 m/s;
Weight - 2,7 kg.
When installing the antenna, it is desirable to adjust. To do this, by measuring the SWR on the channel you have chosen, set the required length of the coil. If the antenna is tuned lower, the coil is lengthened, and vice versa.
Ris.2
Author: RCB, Moscow; Publication: N. Bolshakov, rf.atnn.ru
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