Practical designs of DJ9BV antennas for the 144 MHz band. Scheme, description

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Practical designs of DJ9BV antennas for the 144 MHz band. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / VHF antennas

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The purpose of the article published below is a brief analysis of the current state of antenna-feeder technology and a description of the practical design of a simple, efficient and technological antenna developed by the famous German ultrashortwave Ponter Hoch (DL6WU), which was modified and brought to high manufacturability by Rainer Bertelmeyer (DJ9BV), who has been for many years the "legislator" of European novelties in terms of VHF technology [1,2].

Among the variety of VHF antennas used for amateur radio communications [3, 4], a special place is occupied by "wave channels" with an elongated traverse (boom), as the easiest to manufacture, non-critical to tuning, allowing you to get a large gain and a decent radiation pattern. In addition, they can be used to create a complex highly efficient antenna-feeder system for conducting radio communications across the Moon.

In table. 1 shows the main characteristics of the most common "wave channels" for the two-meter range. As can be seen from it, there is a tendency to improve the parameters of the antenna with an increase in the length of the traverse. A significant difference in relation to F / B (forward / backward") is caused by the use of complex reflectors in some cases.

Table 1

Antenna Boom length, m, (part of the wavelength) Gain, dB Radiation pattern, radius, in-plane F/B ratio, dB Development author
E H
DJ9-2-1,8 3,75 (1,8l) 11,2 39 44 20,2 DL6WU
TONNA-13 4,42 (2,13l) 11,35 36,3 40 17,5 F9FT
DJ9-2-2.1 4,44(2,1l) 11,8 36,8 40,5 24,2 DL6WU
YU0U 2x3,63 (3,5l) 11,95 37 33,5 33 YU0B
TONNA-16 6.34 (3,1l) 12,65 34 37 21 F9FT
TONNA-17 6,545 (3,2l) 12,9 33 35,7 30 F9FT
DJ9-2-3.2 6,69 (3,2l) 13,25 31,2 33,5 20 DL6WU
TONNA-17 6,545 (3,2l) 12,9 33 35,7 30 F9FT
DJ9-2-3,6 7,5 (3,6l) 13,6 30 31,75 20,8 DL6WU
DJ9-2-4,0 8,34 (4,0l) 14 29 30,5 24,3 DL6WU
LBX-16 8,509(4,1l) 14,05 28 29,5 22,6 DL6WU
DJ9-2-4.4 9,18(4,4l) 14,3 28 29,5 21 DL6WU
LBX-17 9,35 (4,5l) 14,4 27 28,5 20 DL6WU
DJ9-2-4.8 10,02 (4.8l) 14,6 27,5 28,8 22 DL6WU

All "wave channels" on the VHF bands can be conditionally divided into three types according to the way the elements are arranged on the traverse: they can be electrically connected to a metal boom, isolated from it, or located on a non-metallic boom. Each type has its own "boom effect" - the degree of influence of the diameter of the boom on the electrical length of the element passing through it. The required geometric length of the element depends not only on the diameter of the boom, but also on the diameter of the element itself. After the publication by K. Fechtel of the description of the antennas "TONNA" (F9FT) in the journal "Radio" [5], many ultrashortwaves of the former USSR repeated these designs, which for a long time became a kind of standard for VHF antennas. Along with the ease of manufacture, these designs have a number of significant fundamental drawbacks. First, the lack of matching and balancing casts doubt on the possibility of obtaining a "pure" radiation pattern. Secondly, the elements located on the boom are electrically connected to the latter. Any mechanical connection does not guarantee long-term reliable electrical contact of heterogeneous metals (even aluminum - duralumin). The absence of element-boom contact or its unstable nature leads to a change in the antenna parameters (increase in SWR, diagram distortion, noise). Thirdly, if there are no boom materials at hand and elements that fully correspond to the description, then the use of random materials does not allow you to get the expected results.

The proposed design of the DJ9BV antenna is free from these shortcomings. In table. 2 shows the main geometric dimensions of this antenna, in it R denotes a reflector, DE is a vibrator, D is a director.

Table 2

Element Length,
mm Distance between
elements, mm Distance from zero
marks, mm Note
R1..R2 1083 - 0 Double for 4,8l
R1..R2 1053 - 0 Double for 1,8l, 3,2l
R 1030 - 0 For 2,1l, 3,6l, 4l, 4,4l
DE 990 360 360 Vibrator dia. 8 mm
D1 950 165 525
D2 940 375 900
D3 930 450 1350
D4 920 525 1875
D5 915 585 2460
D6 910 630 3090
D7 905 660 3750 DJ9-2.1.8
D8 900 690 4440 DJ9-2-2.1
D9 895 720 5160
D10 890 750 5910
D11 885 780 6690 DJ9-2-3.2
D12 880 810 7500 DJ9-2.3.6
D13 875 840 8340 DJ9-2.4.0
D14 870 840 9180 DJ9-2-4.4
D15 855 840 10020 DJ9-2-4.8

Antennas 2,2l, 3,6l, 4,0l, 4,4l long have a single reflector, 1,8l, 3,2l, 4,8l long have a double reflector that increases the forward / backward radiation ratio. The boom is made of a duralumin square section with dimensions of 20x20x2 mm. The elements are made of 4 mm duralumin rod. The vibrator is made of an aluminum tube with an outer diameter of 8 mm and a wall thickness of 1 mm. The design of the active vibrator is shown in fig. 1. The middle point of the vibrator can be electrically connected to the boom.

Practical designs of DJ9BV antennas for the 144 MHz band
Ris.1

The matching U-elbow is made from a length of 680 mm coaxial cable with a characteristic impedance of 50 ohms. Particular attention should be paid to the reliability of the waterproofing of the junction of the vibrator with the U-elbow and the feeder.

The design of a vibrator with a resistance of 300 Ohm is described in [6].

The placement of reflectors is shown in Fig.2.

Practical designs of DJ9BV antennas for the 144 MHz band
Ris.2

With a boom diameter of more than 20 mm, the length of all passive elements must be increased by 1 mm at a diameter of 25 mm, by 3 mm at 30 mm, by 6 mm at 40 mm. Subject to adjustments for the length of each element, the boom can be made from pipes of various diameters. The use of a telescopic boom increases the mechanical strength of the structure. If the diameter of the passive elements is 5 mm, the lengths of all elements must be reduced by 4 mm. Passive elements must be reliably isolated from the carrier beam.

Options for placing elements are shown in Fig.3.

Practical designs of DJ9BV antennas for the 144 MHz band
Ris.3

Figure 3a shows the DJ9BV variant, in fig. 3b - RW3TJ. In the first case, standard nylon bushings with a 4 mm diameter hole were used. In the second, 5-mm elements and pieces of tubes made of stabilized polyethylene are used (sheath of the PK75-4-12 coaxial cable).

The electrical parameters of various antenna options at a frequency of 144,5 MHz with an SWR of at least 1,2 are given in Table. 3.

Table 3

Antenna type Gain, dB F/V ratio, dB Directional pattern, degree Distance, m, in plane
E H Е Н
DJ9-2-1,8 11,2 20,2 39 44 3,10 2,77
DJ9-2-2,1 11,8 24,2 36,8 40,5 3,29 3
DJ9-2-3,2 13,25 20 31,2 33,5 3,86 3,6
DJ9-2-3,6 13,6 20,8 30 31,75 4 3,79
DJ9-2 4,0 14 24,3 29 30,5 4,14 3,94
DJ9-2-4,4 14,3 21 28 29,5 4,29 4,07
DJ9-2-4,8 14,6 22 27,5 28,8 4,36 4,17

The columns "Distance E" and "Distance H" indicate the optimal distances between antennas in the vertical and horizontal planes in the manufacture of antenna arrays. Dimensions can be changed within the range from 80 to 105% of those indicated in the table. Reducing the size allows you to improve the radiation pattern, and increasing - to increase the gain. The four antennas DJ9-2-4,0 gives a gain increase of +5,9 dB in relation to a single one, the total gain of such an antenna is 20 dB.

The author of the article made and tested four designs of DJ9BV antennas. DJ9-2-3.6 antennas have been operated for a long time at the UZ3TXB radio station, were used in the UW3TJ / A and RU1R expeditions. The DJ9-2-4,4 antenna showed excellent results in the UA1C expedition, allowing the VHF team of the RRR Committee to show the best result in the "VSS-93" contest.

The author expresses his deep gratitude to DJ9BV for the kind permission to use the results of his work [2] and expresses confidence that this publication will enable ultrashortwave workers to manufacture highly efficient antennas and antenna systems.

Literature

1. Gunter Hoch (DL6WU). Extreme lange Yagi-Anicnnen. - UKW-BERtCHTE. 1992, No. 1.
2. Rainer BcrlelmeBter (DJ9BV). Yagi-Antennas for 144 MHz.-DUBUS. 1990. No. 1.
3. Spindler. ANTENNEN. - VEB VERLAG TECHNIK BERLIN, 1981.
4. Benkovsky Z., Lipinsky E. Amateur antennas of short and ultrashort waves. - M-: Radio and communication. 1983.
5. Fechtel K. (UB5WN). High performance VHF antennas. - Radio, 1983, N 3.
6. Kharchenko V. (RB4EXN). Vibrator DJ9UV-1-ONG-YAG1. Radio amateur. 1991, No. 6.

Author: Oleg Arkhipov (RW3TJ), Nizhny Novgorod; Publication: N. Bolshakov, rf.atnn.ru

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