Description ( continued from 2E):
Synthesis of theoretical horizontal patterns
By using a directional antenna consisting of 4 towers many different horizontal patterns can be tuned provided that current distributions of corresponding amplitudes and phases can be realized on the towers. The tower with its upper and lower rope cages represents a thick radiator and simple theories for slim radiators can not be applied. Computer programs basing on the Method of Moments (MM) enable us to calculate antenna configurations with all details taking into account the coupling of radiation. For arrays of complex radiators, like the one of Radio Vatican, a “direct" synthesis of the pattern with MM calculations at every step of optimization is not feasible, because the calculation time would be much too high. "Direct" means to vary the feeding voltages (amplitude and phase) of all towers as long as the right pattern is obtained. This is nearly impossible. Therefore a method was developed to determine the voltages at the feeding points and the currents on the towers from the given patterns.