VHF antenna. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / VHF antennas
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Many VHF stations in Poland use an antenna designed by DL7KM. The antenna shown in Fig. 1, I observed in the field. With its relative compactness, it showed results no worse than the nine-element SP6LB. It is powered by a 50 ... 60 ohm cable.
The vibrator can be made from a tube, angle or tape. It is fixed on insulating racks. In fact, it is recommended to make it from copper and solder all the joints, although this is not a prerequisite.
Fig. 1
A whole family of these antennas is described in Zdzisław Bienkowski's book "Poradnik Ultra Krotko Falowca" (literally "hint, assistant" of the ukavista), published in Warsaw in 1988 with a circulation of 10 copies. Figure 2 shows an antenna with reflectors. Parameters - according to the book aE=670,aH=540. Gain G=9nE. Two such antennas should theoretically have a gain of 12 dB, but in practice 11,5 dB is achievable. Input impedance X1 X2 - approximately 60 ohms. In principle, this allows you to feed them with both a 50 ohm cable and a 75 ohm cable.
Ris.2
Figure 3 shows the power supply of two antennas. The pieces of cable 1a can be quite long. At a distance of 0,095l (130mm) from the tee, an open cable 130 mm long is placed, although the DL7KM itself gives a distance from the tee of 108 mm, and the length of the side cut is 133 mm with a 60 ohm cable.
Ris.3
The antenna shown in Fig.4 has parameters: G=13dB, aE=350, aH=320, F/B=25dB.
Ris.4
Fig. 5
Author: C.Popovich, (UC2LAQ); Publication: N. Bolshakov, rf.atnn.ru
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