Modelling real practical antennas - guidelines and tips from code users' notebooks

The computational electromagnetics (CEM) code NEC-4 has been validated, and its use demonstrated as an aid in the design of complex monopole antenna systems. The value of the model in understanding how to tune the antenna, and what trends to expect is enormous. MININEC cannot be used to model real Earth beneath the antenna, but our study shows that the prediction of base impedance is precise enough for coupling unit design purposes if base capacity is taken into account, and the vertical radiation patterns (VRPs) predicted with change in model parameters show the right trend. This paper considers only MF antennas for broadcast application, since the purpose of the paper is to compare numerical modelling with measurements in full scale, a study is needed to validate methods of modelling and the NEC code. The results obtained and the techniques developed can of course be applied to any frequency, suitably scaling frequency and antenna size.