Eight-element antenna of the Wave channel type. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / VHF antennas
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The Czech radio amateur OK1DE designed an eight-element "wave channel" antenna, which effectively operates in the range of 144-146 MHz. The technical characteristics of the antenna are given in the table, the curves for changing the input impedance over the range are shown in Fig. 1, and the radiation pattern in the horizontal plane is shown in Fig. 2.
Ris.1
Antenna technical data:
- Number of elements......8
- Gain (compared to conventional dipole), dB.......11-12
- Weakening of the rear lobe, dB.......14±16
- Traveling wave coefficient ....... 0,4-0,7
- Maximum length, m......3,81
- Maximum width, m.......1,135
Ris.2
The antenna device and its dimensions are shown in Fig.3. Dimensions are in mm. When building an antenna with dimensions that are given outside the brackets, its input impedance will be 300 ohms. In the event that it is necessary to have an input impedance of the antenna of 150 ohms, some of its dimensions change and are given in brackets. The material for the manufacture of the antenna is duralumin tubes: for all elements with a diameter of 10 mm, and for the rails on which the elements are fixed, with a diameter of 28 mm.
Fig.3 (click to enlarge)
An active loop vibrator is used in the antenna. It is easiest to bend such a vibrator in a cold way as follows. Two rollers with a diameter of 43 mm are machined from solid wood and fixed on a thick board. The distance between the centers of the rollers must be 900 mm. The tube intended for the vibrator is applied to the rollers, strengthened so that it does not move, and bent around the circumference of the rollers.
The antenna elements are fixed on the rail with M3 bolts as shown in Fig. 4. In order to avoid deteriorating the performance of the antenna, all dimensions indicated in Fig. 3 must be strictly adhered to, as well as the thickness of the tubes and the method of fastening the elements and rails.
Ris.4
In order to be able to use the most common cables with a wave impedance of 75 ohms (RK-1, RK-3) for the antenna feeder, it is necessary to connect the loop vibrator of the antenna with an input impedance of 300 ohms U - knee (Fig. 5, a), which is simultaneously with transformation of the input impedance of the antenna will symmetrical it. The transformation of the input impedance of the 150 ohm antenna is carried out using a transformer made of a cable.
Ris.5
Such transformers are described in the article by Kharchenko and Isupova "Incomplete zigzag antenna" ("Radio", 1965, No. 1, pp. 24-27 and page 4 of the tab in the magazine). The length ltr of the transformer for this antenna is 342 mm. To balance the antenna, the feeder with the transformer is laid along the tube of the loop vibrator to the point of zero potential (Fig. 5, b). The outer insulating sheath is not removable from the cable. In this case, it is more convenient to attach the loop vibrator to the rail with the open side up (that is, the side to which the ends of the transformer are attached).
Literature
- Radio No. 2 1966, pp. 57-58
Publication: N. Bolshakov, rf.atnn.ru
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