ANTENTOP- 01- 2012, # 016

Ground Plane Antenna for 40, 20, 15 and 10- meter Bands

Vsevolod Vorob'ev, UA3FE, Moscow

Credit Line: Radio 1958, #6, pp.: 30, 31, 36

Originally the antenna was used (and described) by polish ham Kahlickiy in 1946 year. The advantage of the antenna is that only one relay is used to switch the four working bands of the antenna. Vertical radiator of the antenna is grounded so the antenna may be used near lightning storm period.

To understand how the antenna is matched and tuned we need to review some pieces of the antenna theory. Let's see to the Figure 1 and Figure 2. Figure 1 shows "active antenna input resistance" vs "ratio antenna length/working wavelength". Figure 2 shows "reactance of antenna input impedance" vs "ratio antenna length/working wavelength". The diagrams are simulated for vertical radiator placed above ideal ground. However, 4- counterpoises with length equal to the vertical part of the antenna are satisfactory analogue of an ideal ground.

Radio # 6, 1958

Based on the Figure 1 and Figure 2 it is possible to find antenna impedance of the vertical radiator Vs of the length of the vertical. When the physical length of the vertical radiator is the value that is multiplied by the 0.25 lambda, the input impedance of the radiator is only resistive. Radiator has inductance reactance in the input impedance at the physical length from 0.25 to 0.5- lambda. Radiator has capacitance reactance in the input impedance at the physical length from 0.5 to 0.75- lambda. And so on.

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