When making a KB antenna, you can win in gain. Scheme, description

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When making a KB antenna, you can win in gain. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / HF antennas

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In the manufacture of a KB antenna, gain can be gained if the usual double-square antenna frame is converted into a rectangular one, as shown in Fig. one.

When making a KB antenna, you can win in gain
Ris.1

Active, or radiating, are the vertical sides of the antenna. To increase the efficiency, it is advantageous to make them from duralumin tubes with a diameter of 10-20 mm. The horizontal sides - reactive - complement the perimeter of the rectangle to the resonant length and are made from a conventional antenna cord. The upper side is torn exactly in the middle by a nut insulator so that the current distribution in the frame does not depend on the feeder connection point, by changing which you can match the antenna with any cable. The input impedance of the frame varies from 30-40 ohms (the feeder is connected in the corner of the frame) to several thousand ohms in the center of the horizontal side. The feeder is laid along the antenna conductor and is retracted at a right angle in any direction from the middle of the vertical side, that is, at the current antinode point. For complete balancing, it is desirable to connect the cable braid at this point with the antenna wire.

In terms of radiation characteristics, the "Rectangle" is close to a two-element in-phase antenna (gain of about 2-3 dB), but has a relatively narrow operating frequency band - 2% on the 20 m band. On fig. Figure 2 shows for comparison the radiation patterns in the horizontal plane of the double square frame with vertical polarization 1 and the described antenna 2. Spurious lobes are practically absent due to the small distance between the reactive sides of the frame.

When making a KB antenna, you can win in gain
Ris.2

Due to its low height, the "Rectangle" seems to be very convenient for ranges of 40, 80 m. It must be installed so that there are no shading objects nearby. The distance from the lower wire to the roof can be several tens of centimeters. To obtain a unidirectional diagram, you can use the same frame configured as a reflector or director, spaced 0,05-0,15 l from the first. In the case when the height of the antenna is critical, "Rectangle" can be successfully used on high-frequency bands as part of multi-element directional antennas. The characteristics of such a three-element system are similar to those of a four-element Uda-Yaga type antenna.

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