Something about antennas. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Antennas. Theory
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... if instead of one resonant reflector in a "wave channel" ("VC") type antenna, two similar ones are used, but located one above the other at a distance of 0,3 wavelengths, the gain (Kus.) will increase by 0,3 dB at constant antenna length [1; 2; 3].
... by placing 3 reflectors in a circle with a radius of 0,3 of the wavelength from the active vibrator, except for the increase in Kus. antennas, the suppression of the rear and side lobes of the radiation pattern (DN) improves [2; 5].
... using instead of the above-described reflectors a square reflex grating with a side length of at least a wavelength, Kus. "VC" can be increased by 2 -ZdB [1].
... To increase Kus. "VK" by 3 dB (twice in power), the length of the antenna must be increased by 2 times. However, in the so-called. "antennas with backward radiation", when using an additional reflector array (located on the side of the directors at a distance of 0,25 wavelength), the "electrical" length of the antenna is doubled and Kus is increased. with a slight increase in the length of the "physical" [1; 2; 6].
... in multi-element "VK" the resistance of the loop vibrator (300 Ohm) is significantly reduced, and, in the case when it is equal to 75 Ohm, it becomes possible to connect the coaxial cable of the feeder directly to the vibrator terminals without matching devices. Some “skew” of the pattern that occurs in this case is almost completely compensated by the influence of a large number of antenna directors. The loop vibrator, in such an inclusion, must be isolated from the supporting structure [2; 5].
... Kus. HB9CV antennas can be increased by 1 - 2 dB by choosing the optimal suspension point, which provides the summation of the radiated direct wave and the common mode wave reflected from the ground (or surrounding objects) [1;2].
... log-periodic antennas (LPA) have the widest range of operating frequencies, and therefore the LPA gain is always 1 - 6 dB less than the "VK" gain with the same number of elements.
... the gain of the "square" with the number of elements X is approximately equal to the gain of the "VK" with the number of elements X + 1 [6].
... the element of the loop antenna in the form of a circle has Kus. more than that of the "square", and the largest Kus. has an element in the form of an ellipse with a ratio of horizontal and vertical diameters of 1:3 [3; four). This is explained by the fact that in these designs there are no corners that cause the appearance of reflected waves at the bending points, which degrade the parameters of the antenna.
... the antenna amplifier (AM) located on the antenna can be damaged (even with the power turned off) by electrostatic charge formed on the antenna terminals, for example, during a thunderstorm. Such a defect can be prevented by shunting the AU input with an RF inductor, which galvanically closes the antenna terminals, but does not affect the operation of the AU.
Literature:
1. K. Rothammel. Antennas. -M.: Energy, 1979.
2. Z. Benkovsky, E. Lipinsky. Amateur antennas KB and VHF. - M.: Radio and communication, 1983.
3. Radio, television, electronics (NRB) N12/79, p.7; N l/80, p.5; N12/81, p.6; N4/87, p.10.
4. Radioamator (SFRY) N4/81.C.129.
5. Radio electronics (PNR) N6 / 80.C.149.
6. Radio. No. 2/62, p.26; No. 6/76, p.20; N7/76, p.26.
Author: K.Smirnov, Makeevka; Publication: N. Bolshakov, rf.atnn.ru
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