PAPER TITLE :AN IN-SITU INVESTIGATION OF ABNORMAL PROPAGATION CONDITIONS AT NSUKKA, NIGERIA

JOURNAL Of SUSTAINABLE TECHNOLOGY | VOLUME 2 NUMBER 11 2011

Paper Details

  • Author(s) : FALODUN S. E.
  • Abstract:

In commercial radio link planning, the statistical probability of occurrence of propagation events such as super-refraction, sub-refraction, and ducting are estimated for the link design of communication circuits. Since these phenomena vary for different propagation zones, it is important to determine the values for each locality. The basic data employed for this study were meteorological data of atmospheric pressure, temperature, and relative humidity obtained by in-situ measurements at Nsukka, (7.40E, 6.90N) Nigeria. Wireless meteorological sensors were positioned at the ground surface and at 100m altitude on a communication mast. The measurements were made every thirty minutes and round the clock for a period of two years (February 2007 to March 2009). Statistical distributions of the refractive index modulus, its vertical gradient, and the diurnal and seasonal variations of the refractivity modulus were determined from the measured data. The obtained results have been used to designate the refractivity profiles as sub-refraction, super-refraction, and ducting. The refractivity values at the station have shown that the surface layer is super-refractive most of the time with higher probability of occurrence of ducting during the rainy season. However, super-refractive conditions is predominant during the dry season. The results also show that the values of the refractive modulus at 100m altitude were higher in the morning and late evening hours while they show minima during the afternoon hours. The worst propagation condition (when possible signal outage due to propagation effects) is in the afternoon within the time window from 15:00 to 18:00 hrs when refractivity values are the lowest. Also deduced is the value of the effective-earth-radius factor, k, which is representative of south-eastern Nigeria.