GROUND-WAVE RECEPTION AND GROUND CONDUCTIVITY

By

Author

Presented To

Department of Engineering

ABSTRACT
This investigative research consists of three parts: Plotting of theoretical propagation curves with the aid of computer, determining the effect of the variation of the ground conductivity on ground-wave field strength and deduction of the ground conductivity. Theoretical ground-wave propagation curves were plotted for flat earth with the aid of a digital computer for some broadcast frequencies in use in the Northern States of Nigeria, Computer CALCOMP programmes were developed for the plots. The effect of the variation of the ground conductivity on ground-wave field strength was investigated by measuring the field strength radiated from MW radio stations for five months, March - July, 1981. The measurements showed that the radiated field strength was practically constant irrespective of whether it was rainy or dry season. One of the conclusions from the measurements was that as the variation of the ground conductivity and vegetation have opposite effect on ground wave the effective influence of the variation of ground conductivity could be so small that it could not be detected with the field strength meter. The field strength increases with increase in the ground conductivity while vegetation attenuates ground wave. The determination of the ground conductivity in the northern parts of Nigeria was carried out by the attenuation technique. The ground resistivity method was used in Samaru - Zaria to confirm the result obtained there by the attenuation technique. According to the research results, 2, 3» and 4 mmho/m were obtained as the ground conductivities in parts of Kaduna State; 3 mmho/m was obtained in Kano State; 2 mmho/m was the value obtained in Niger State. 3 and 4 mmho/m were obtained in Sokoto State. A CALCOMP programme was used in plotting the measured field strength on the theoretical propagation curves. All the CALCOMP programmes used in this research can be found in the Users' Manual of the CALCOMP Programmes for Plotting Theoretical Ground-Wave Propagation Curves written by the author.