Effective Earth radius factor characterization for line of sight paths in Botswana

The ITU has adopted new methods for predicting the deep-fading distribution due to multipath propagation for the average worst month over UHF and SHF terrestrial line-of-sight links. These methods employ refractivity gradient statistics available from world maps, and are recommended for application in all regions of the world. In this regard, significant progress in the global climatological modeling of the main propagation effects in clear-air and precipitation conditions have been reported (Olsen, R.L. and Tjelta, T., IEEE Trans. Anten. and Propag., vol.47, no.1, 1999; Olsen, Proc. 3rd Regional Workshop on Radio Communications in Africa, 1999), with an attempt to relate the results to the African continent. D.C. Baker and A.J. Palmer (see Trans. SAIEE, vol.93, 2002) have proposed a model for the cumulative distributions of the fraction of times of occurrence for certain values of the k-factor for South Africa. They have assumed, based on earlier reports, that a normal distribution for the pdf of the k-factor is appropriate. We develop an empirical model for the k-factor distribution based on radiosonde data for Botswana. We model the distribution for the months of February, May, August and November, as per ITU-R practice, at height ranges of 0-500 m and 0-200 m above ground level