Measurements of path losses over irregular and woody terrain at 61 MHz compared with propagation predictions given by various models

Measurements of path losses have been performed over irregular and woody terrain at 61 MHz in order to be compared with predictions given by various models. Experimental setup and procedures are first described then we report results concerning two types of terrain: meadows and forests. For open terrain the agreement is satisfactory in spite of some irregularities. The best fit of the experimental data is obtained with an original integral equation method. For woody paths, the measured field has a chaotic behaviour. The complexity of the phenomena is related to the fact the wavelength is comparable with the characteristic lengths of the medium and only statistical approaches could be relevant. We found that classical empirical models overestimate the additional attenuation due to vegetation.