Shortened antenna range 160 meters. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / HF antennas
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Shortwavers often have difficulty installing full-size antennas for operation on the low-frequency KB bands. One of the possible versions of a shortened (about two times) dipole of the 160 m range is shown in the figure. The total length of each halves of the emitter is about 60 m. They are folded in three, as shown schematically in Figure (a) and are held in this position by two end (c) and several intermediate (b) insulators. These insulators, as well as a similar central insulator, are made of a non-hygroscopic dielectric material with a thickness of approximately 5 mm. The distance between adjacent conductors of the antenna web is 250 mm.
A coaxial cable with a characteristic impedance of 50 ohms is used as a feeder. The antenna is tuned to the average frequency of the amateur band (or its required section - for example, telegraph) by moving two jumpers connecting its extreme conductors (in the figure they are shown by dashed lines), and observing the symmetry of the dipole. Jumpers must not have electrical contact with the center conductor of the antenna.
With the dimensions indicated in the figure, the resonant frequency of 1835 kHz was achieved by installing jumpers at a distance of 1,8 m from the ends of the web. The standing wave coefficient at the resonant frequency was 1,1.
Data on its dependence on frequency (i.e., on the bandwidth of the antenna) are not available in the article.
Author: Di Rocco; Publication: N. Bolshakov, rf.atnn.ru
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