Dry Hot and Cool Tropical Climate Attenuation models at VHF

This paper presents the experimental investigation of VHF (92.1MHz) radio wave attenuation due to the effects of dry hot and dry cool weather conditions plus the effects of ground and tree-canopy reflections (GCREFS) in the tropical region. Using the method of least square fit to the measured data, new attenuation models characterizing the VHF radio wave propagation loss during the dry hot and dry cool atmospheric conditions in the region of consideration were obtained. It was shown that the signals suffer more loss during dry cool weather than during dry hot weather. When some existing models were compared with the measured data, it was found that measured data are fairly favorably in agreement with the ground and tree-canopy reflections (GCREFS) plus dry air weather ITU-R model prediction (the normalized root-mean-square deviation~ +0.32%)