Experimental study of VHF propagation in forested environment and modelling techniques

Measurements are carried out to study different aspects of the propagation of VHF radiowaves in a forested environment. In order to model the evolution of the spatial average of the received signal inside and outside the vegetation we find that good agreement can be obtained with the following method: in the forested areas, the actual Earth ground is replaced by the top of the canopy to compute the field; then, the signal inside the forest is the signal on top of the canopy minus an attenuation term due to the vegetation. On the other hand, fast fading phenomena inside the forest seem to be qualitatively explained by a simple model involving the nearest scatterers.