Small three-element antenna. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / VHF antennas
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Two American shortwaves Myers (W1FBY) and Rusgrove (WA1LNQ) developed a small-sized three-element antenna for the 20 m band. A significant reduction in its size was achieved through the use of inductors and capacitive elements. All main dimensions of the antenna are shown in the figure.
The antenna is made of aluminum tubes with an outer diameter of 32 mm. The frames for winding the coils are connecting inserts with a diameter of 28.6 mm, made of organic glass. Coils L1, L2 contain 23,5 turns, L3, L4 - 29 turns, L5, L6 - 26 turns of wire (in enamel insulation) with a diameter of 1.4 mm. The winding length of all coils is 229 mm.
The capacitive elements are in close proximity to the coils. They are pieces of aluminum corners with a side of 90 mm and a length of 19 mi attached to the tubes (at an angle of 610 ° to each other). The ends of the corners are connected with a wire with a diameter of 1,5-2 mm. The resonant frequencies of the elements are shown in the figure.
Coordination of the antenna vibrator with the feeder is carried out using an L-shaped device. The diameter of the tube used in the matching device is 9,5 mm, its length is 1016 mm. The supporting insulating insert (not shown in the figure) is made of organic glass. The maximum capacitance of the trimmer capacitor is 140 pF. It is placed inside an aluminum box and isolated from the walls. The capacitor is connected to the tube with an aluminum strip 152 mm long.
Setting up a properly assembled antenna is reduced to obtaining a minimum SWR at a frequency of 114,1 MHz using a trimmer capacitor and the position of the shorting collar in the matching device. The SWR value at the edges of the range should not exceed 2.
Literature
- "QST" (USA), 1974, N 10
- Radio #6, 1975
Authors: Myers (W1FBY) and Rusgrove (WA1LNQ); Publication: cxem.net
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