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Further Investigation into VHF Radio Wave Propagation Loss over Long Forest Channel

Alade Olusope Michael

This paper presents the experimental study on the radio wave propagation loss through long tropical forest environments at Very High Frequency, VHF (92.1MHz as a case study). The method of least square was employed to fit the experimental measured data. The measured data were then compared with some existing analytical and empirical radio propagation loss models, namely: Free Space Attenuation (FSA), Ground Reflection (GR) and Canopy-Ground Reflection (CGR), CGR plus foliage (ITU-R model) and CGR plus foliage (Weissberger model). CGR model provides the best fit for the propagation loss at VHF (92.1MHz) over long tropical forest. CGR model has minimum Normalized root-mean-square deviation, NRMSD = 0.106%. NRMSD between the measured data are the other existing models are: FSA~0.828%, GR~0.122%, CGR plus foliage (ITU-R)~0.410% and CGR plus foliage (Weissberger)~0.668%. The results obtained therefore shown that the radio wave propagation loss in the channel of consideration is due to tree-Canopy and Ground Reflections (CGR) rather than the foliage induced effect.