HF Helical Antennas: Theory and Practice

I took the bandwidth as sum two frequencies one lower another high the resonance frequency where input impedance of the antenna changed twice. Figure 9 shows the way to find the bandwidth. Of course, maybe such assuming not strictly right but for my homebrew measuring equipment it is the solution. Take attention that the plot is asymmetrical. As usual the bandwidth of the antenna is a little wider to the side of the high frequencies.

Figure 10 shows Q of the experimental helical antennas. The plot shows Q for helical antennas with shortened factor from 2 to 10. Helical antennas with high shortened factor are very difficult to analyze because the behavior depends on the nearest objects, on the dielectric form and so on.

Figure 9 Way to Find the Bandwidth

Figure 10 Q of the Experimental Helical Antennas Vs Shortened Factor

www.antentop.org

Page- 17