Monopole antenna above a hemisphere

Antenna imaging by a finite ground is investigated analytically and numerically by considering a conical monopole antenna above a finite hemispherical ground of variable radius. The ratio
Y_{t}/Y_{t \infty}
of the terminating admittance of the antenna over a finite to that over an infinite ground is evaluated and plotted versus the ground radius for various monopole lengths. The plots provide a quantitative measure of the effectiveness of finite screens in imaging antennas.