Contours for an HF antenna
Among Soviet and foreign Amateurs quite widespread like w3dzz dipole antenna, which works well for receiving and transmitting, pretty simple to manufacture and is in good agreement with the widespread 75 Ohm cables RC-1 and RC-3.
On the ranges (14,21 and 28 MHz) antenna has a complex pattern, with almost equal success to work in any direction.
The scheme of such antenna with dimensions is shown in Fig. 1.
Many Amateurs deterred by the seeming complexity of manufacturing embedded in the fabric of the antenna circuits, which are rather high demands moisture resistance, mechanical and electrical strength.
The manufacture of such circuits and the subject of this article. The lids of two identical plastic boxes (you can use boxes for sandwiches) are mounted capacitors 62 pF and inductance at 8.2 µh. Under the additional capacitors placed on a sheet of mica.
The findings from the contours are carried out through the ceramic bushings (the authors used the bushings from the antenna flap radios SCR), and the contours used a constant air capacitors from the same station, collected on a ceramic base with square plates 50X30 mm. you Can apply the capacitors and other type, but their capacity must be equal to 62 pF, and the breakdown strength of not less than 2.5-3 m
Coils are wound with wire PEL 2.0 and for greater rigidity mounted on a laminated bakelite plate. Each coil contains 27 of turns, the winding diameter is 30 mm, the winding length of 75 mm.
More precisely, the inductance and capacitance of the circuit can be selected with the help of LC bridge, but good results are obtained without such precise settings; each circuit to be configured using the gear on the frequency 7,05 MHz by changing slightly the length of the winding coil.
For increasing the mechanical strength of the box on the gap on its upper surface superimposed plate PCB thickness 1.5 to 2 mm Through it and the lid of the box are tubular bushing bolts ceramic insulators.
Head through bolts are laid brass plate, which after pre-twist segments are soldered antenna cord is desired length. Under the nuts of these bolts laid double petals, to which is soldered the parts of the circuit.
For protection bushing insulators of ceramics from pollution and precipitation they (individually) covered textolite circles with a diameter of 90 mm.
In the bottom cover to prevent the accumulation of condensed moisture on the edges of her six holes are drilled with a diameter of 2-3 mm.
The halves of the box are held together by the binding of adhesive tape or nylon cord. All outside parts of the bolts and soldering nitroenamel or painted over with BF-2.
Antenna feeder cable RK-1 and RK-3 is used successfully by the authors. In low passage have conducted a large number of links as the Telegraph and telephone to all the continents with the help of transmitters 100 watts,
SWR Showed that the ranges of 7, 14, 21 and 28 MHz does not exceed two, and the range of 3.5 MHz - no more than three.
The disadvantage of the antenna is its great length (about 34 km), with a significant weight of the cable feeder forced to put her on three pillars.
Authors: A. Ilyin (UB5PB), N. Sopron (UB5YE), Cherkassy; Publication: www.cxem.net