ANTENTOP- 01- 2010, # 012

Directional Helical Antennas

I..Kapustin, UA0RW

Radio # 7 1958, pp.: 34-35.

The antenna intended for the 20-meter Band. Figure 1 shows the design of the antenna. There are two Voltage Fed Helical Dipoles that fed with phase shift in 90 degree.

Figure 1 Directional Dipole Helical Antenna

The distance between the Helical Dipoles is Lambda/4. A Helical Dipole made of two plastic tubes in 3-cm diameter (it is possible to use wood rectangular 3x3- cm) and 110-cm in length. Two spirals in 77 turns of wire cord in 3-mm (9-AWG) diameter are coiled above the each tube. Gap between near coils is 7.5-mm. Ends of the dipoles (made from tubes) are plugged by wood. In the plug a copper tube by length in 45-cm and 8-mm OD is inserted. Antenna wires are soldered to the copper tube near the plug. Bare wire (or tube) with OD that can fit inside the copper tube is inserted into. Antenna is tuned into resonant by moving the bare wire. Figure 2 shows the design of the tube ending.

The Helical Dipoles are fastened to a traverse made from a strong square wood stick. The stick is fastened to an antenna mast. Open Wire Line made of copper cord wire (3- mm (9-AWG) OD), the distance between wires is 6-cm. The line is sitting on insulators under the strong square stick. Length of the line is 5.2- m. Design of the Directional Dipole Helical Antenna is shown on Figure 3.

Front Cover of Radio #7 1958

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