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

Plots are presented, of the radiation efficiency and input impedance of a thin quarter-wave monopole element with a radial wire ground plane in proximity to flat lossy earth, as a function of the number and length of the radial wires, earth permittivity, and location of the earth's surface with respect to the ground plane. The method of moments models have certain advantages over models based on Monteath's compensation theorem or Sommerfeld's attenuation function. These advantages are as follows: current on the ground plane is determined rather than approximated by that for a perfect ground plane; results are valid not only for moderately-large ground planes but for electrically-small ground planes; directive gain and radiation efficiency can each be determined separately rather than being lumped together as a product to yield the antenna power gain; ground plane edge diffraction is not neglected; and analytical conditions on evaluating Sommerfeld's integral are avoided.