Comments on the performance of VHF vehicular radio sets in tropical forests

Some of the effects of tropical forests (jungle) on the performance of VHF radios have been explored. To better understand average propagation effects, the dielectric constant and the conductivity of selected forests have been measured. The effect of forests on the gain and pattern of simple VHF antennas has been explored, as well as signal loss along a trail. Scattering of VHF radio waves by nearby trees has been found to be a significant factor affecting received signal strength at any given point down a forest trail. Comparisons between propagation inside and outside a forest have been made. The results of the measurements have been applied to a determination of the performance of vehicular radio sets. A new concept of effective range of VHF radios operated in a forest is presented; its performance criterion is word intelligibility.