Comparison of computer modelled monopole element with both 120 buried ground radials and 4 elevated ground radials at various heights using NEC-81 versus measured field data in the standard AM broadcast band at 1 MHz

It has been proposed that the use of a small number of ground radials elevated above the surface of the earth can yield similar or actually better radiated performance than a larger number (typically 120) of buried ground radials in the case of a monopole element used in the standard AM broadcast band. This proposal is based on the results of numerous computer modelling. The author knows of no A-B field tests compared to the computed data. A case study is performed at 1 MHz (the center of the standard AM broadcast band) using the NEC-81 computer program modelling both the elevated and buried ground radial scenarios and comparing the findings to the identical measured data. Tower impedances, currents in both the tower legs and along the elevated radials, and radiated fields along one radial and in between two radials at 1 km are presented.