Radiation efficiency and input impedance of monopole elements with radial-wire ground planes in proximity to earth

Results for input impedance are reported with attention given to results for the radiation efficiency of a thin quarter-wave monopole element with a radial-wire ground plane at a small distance above flat earth. Numerical data are appropriated from a method-of-moments optimization of radial-wire ground planes for wire element near earth. Radial efficiency and input impedance are calculated as functions of the number and length of the radial wires. Radiation efficiency is found to increase monotonically with increased numbers of radial wires and increased length of monopole element. As the groundscreen density approaches infinity, the input resistance and input reactance asymptotically approach the values of the disk ground plane. Attention is given to the resonances that appear in input impedance and radiation efficiency for low numbers of radial wires, and the effect is attributed primarily to the fact that the currents on the wires are not closely coupled.