EFFECT OF SECONDARY RADIOCLIMATIC VARIABLES ON SIGNAL PROPAGATION IN NSUKKA, NIGERIA

This study presents the effects of Radioclimatic variables on signal propagation in Nsukka, Nigeria. The primary Radioclimatic data used in the study include temperature, pressure and humidity or water vapour pressure, while secondary radioclimatic data includes refractivity (N), refractive index (n) and effective earthâ€s radius (k-factor). The measurements of the primary variables were made at time interval of 30 minutes daily from August 2013 to July 2014. The results obtained show seasonal variation of the temperature and relative humidity. This leads to the increase in the values of radio refractivity and refractive index. The results also, show that the k-factor values for those months were at the range 1.555 â€" 1.653. This high values of kfactor is an indicator to the possible causes of signal interference in the study area.
KEYWORDS: Refractivity, refractive index, k-factor, Nsukka. 

INTRODUCTION

It has been established that a good knowledge of secondary Radioclimatic data especially the surface refractivity as well as the diurnal and seasonal variability amongst other factors,  are useful tools in planning terrestrial radio links mainly because of multi-path fading and interference effects. Tropospheric surface refractivity poses a major setback to the phenomenon of communication globally. Research done by Oyedun (2007), indicate that the interaction between some tropospheric factors and radio frequencies > 30 Mhz, exposes the signals to important propagation characteristics which often degrades communication links especially at higher frequencies. Korak, (2003) opined that the propagation of electromagnetic waves in the atmosphere (especially the troposphere) is greatly influenced by the composition of the atmosphere, and attributed it  to the fluctuations of atmospheric parameters such as; temperature, pressure and relative humidity. Other important variable, â€�“the tropospheric refractive indexâ€Â� is also a function of pressure, temperature and humidity and this implies that fluctuations of these atmospheric parameters (pressure, temperature and humidity) do cause significant variation in the refractive index of the air in the troposphere. The consequences of this scenario lies in the fact that the signal propagating through the troposphere does not arrive at its destination with the same amount of energy with which it was propagated from the source.  According to Hall (1980), the troposphere can be defined as that region which extends from the earth surface to an altitude of about 10km at the earth poles and 17km at the equator.  Nsukka is located at  latitude 6o 45N and longitude 7o 30E, South â€"Eastern Nigeria. The period of investigation spans across the two major seasons (wet and dry) in Nigeria. This paper aims to investigate the effects of Radioclimatic variables on signal propagation in Nsukka, with a view to establish potential pathways to improve radio/communication signal reception in the study area.