Calculated and measured radiation characteristics of an HF loop antenna mounted upon a helicopter

An HF loop antenna installation on a helicopter is described. The azimuthal radiation patterns at 10 frequencies throughout the HF band are obtained by three methods: mathematical modelling, measurements with a physical scale model, and measurements using the real aircraft in flight. The predictions from the mathematical model were made in advance of any measured results being obtained and no empirically derived information was incorporated into the model. The salient problems connected with each technique are discussed. The results obtained in the study are presented and compared. In the context of HF, the level of agreement between the three methods is considered to be good. The predictions of the mathematical model exhibit a fair degree of consistency with the results of the other two methods.