Three-element directional antenna with vertical polarization. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / HF antennas

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In the practice of amateur radio, antennas with vertical polarization are becoming more common. Specifically, it is possible to single out the high-frequency HF bands and the VHF bands of 144 and 430 MHz, on which this antenna is now often used. This is prompted by a number of significant reasons, including, for example, the need to maintain communication with mobile objects and portable radio stations, difficulties in choosing a place and the lack of the necessary area to accommodate an effective antenna with horizontal polarization, the ability, under certain conditions, to reduce interference with TV reception, if for It uses balanced antennas with horizontal polarization. All this prompts us to look for various ways to improve the efficiency of such antennas.

In particular, all of the above applies to stationary antennas. For these cases, collinear antennas or multi-element directional antennas of the "wave channel" type are often used. Both options, in comparison with simple vertical antennas, have larger dimensions and weight [1,2]. The recently published collection [3] describes a three-element antenna with reduced dimensions. In foreign literature, such antennas are described in more detail [4...8] and have long been known as "HB9RU-Beam". Moreover, the dimensions of these structures are minimal, i.e. elements are made from the calculation of a quarter-wave antenna. Such dimensions allow the use of directional antennas as mobile or portable, made for the VHF bands of 144 and 430 MHz. Moreover, in comparison with the option described in the collection [3], in [4...8] there is no mention of the need to use additional counterweights.

Ris.1

Figure 1 shows the design and dimensions of the antenna, designed to operate on high-frequency HF bands. Its main features are the absence of counterweights, the role of which, obviously, is played by a metal traverse. Adjustable long vibrator allows optimal matching with 50 ohm coaxial power cable. The literature [4,5] provides the main technical characteristics of the antenna:

- gain factor - 7 dB;
- forward-back ratio - more than 15 dB;
- SWR - no more than 1,3 in the bandwidth of about 300 kHz.

A similar design was repeated and tested by the author, but in a stationary version - with a vertical carrier metal mast under the base of the vibrator and two resonant counterweights. Such a technical solution was due to both the specific prevailing conditions and the fear of obtaining an antenna system with low efficiency.

Figure 2 shows the appearance of the tested design. Although it was not possible to confirm all of the above characteristics during the testing of the antenna, it turned out to be quite effective, and the chosen design was resistant to quite adverse natural influences.

Ris.2

Figure 3 shows a variant of the antenna design with gamma matching, proposed in [8] for the VHF bands of 144 and 430 MHz.

Ris.3

Individual elements of this design are shown in Fig. 4 and 5. As a traverse, you can use a corner or a U-shaped profile made of duralumin.

Ris.4

Ris.5

To adjust the elements to a certain resonant frequency, metal screws with nuts are installed at the upper ends of the tubes [4]. All main dimensions and data of the elements of both antenna options are given in the table.

Antenna dimensions and element data

Table 1

Range, MHz	Director D, mm	Vibrator B, mm	Reflector P, mm	Distance A1, mm	Distance A2, mm	Capacitance С1, pF	Distance B1, mm	Length B2, mm	Figure N
14	3560	6980	6120	2110	3170	90	-	-	1
18	2735	5440	4780	1650	2475	90	-	-	1
21	2350	4670	4100	1420	2120	80	-	-	1
24	1990	3960	3480	1200	1800	80	-	-	1
28	1745	3470	3020	1050	1580	70	-	-	1
50	990	1970	1730	595	895	50	-	-	1,2
144	380	520	610	170	287	-	135	45	3
432	126	170	203	56,6	95,6	-	45	15	3

The choice of the outer diameter of the tubes and the thickness of their walls depends on the operating range, i.e. a specific length of the elements, and to a greater extent is determined by the need to ensure the strength of the structure. The most suitable for the manufacture of antenna elements are duralumin tubes. At the same time, the elements, especially the vibrator, are best performed as telescopic ones - from tubes of various diameters. After the final adjustment of the antenna, the position of the tubes is fixed with bolts, as shown in Fig. 2.

Literature

1. Radio, 1980, N3.C.58.
2. KB, 1996, N2, P.38
3. Satellite antennas, KB, VHF, CB, TV, RV. -M.: Symbol-R, 1998., p.238.
4. Radio Amaterske, 1976, N8, p.313.
5. CQ DL, 1975, No. 4.
6. Schlatter E. Three-element vertical beam. OLD MAN 44,1976, H5.R.22-24
7. OLD MAN 46,1978, H1.
8. Rohlander W. HB9RU-Beam for 144 and 430 MHz. - Funkamateur, 1982, N10, p.509.

Author: V.Efremov (UA6HGW); Publication: N. Bolshakov, rf.atnn.ru

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