Abstract:
There has been a downturn in the number of medium frequency - amplitude modulated (MF - AM) broadcasting stations currently operating in Nigeria. This is due to the widespread use of frequency modulation (FM) band for broadcasting and the establishment of more Television stations. Technically speaking, the decline was also motivated by the fact that noise inherent in the AM signal compared to that of FM and TV is huge. This study is aimed at assessing the coverage areas of some MF – AM transmitters over the Nigerian landmass. To achieve this, the electric field strengths of the radio signals were measured along some routes around the transmitters during the rainy and dry seasons and these were interpolated to generate primary, secondary and fringe coverage areas which were geo-referenced on the maps of the owner states. The seasonal variations in the coverage areas were deduced. The study also identified the possible locations of radio beacons for full Advanced Traveller Information Systems (ATIS) coverage of the states. The mean electric field strength in wet and dry seasons are 3.83 ± 0.62 mV/m and 3.06 ± 0.43 mV/m for Oyo Radio, 4.05 ± 0.75 mV/m and 3.04 ± 0.32 mV/m for Kwara Radio, 3.36 ± 0.45 mV/m and 3.89 ± 0.54 mV/m for Voice of Ekiti, and 3.34 ± 0.46 mV/m and 3.13 ± 0.56 mV/m for Federal Radio Corporation of Nigeria. The values are 3.28 ± 0.45 mV/m, 3.88 ± 0.30 mV/m and 3.90 ± 0.82 mV/m around Radio Jigawa, Radio Benue and Kano Radio respectively. Results obtained from the study also reveal that signals from digital MF - AM transmitter provide wider coverage area compared to signals from analogue transmitter of the same transmitter power. It is also revealed from the study that MF - AM signals can still be used satisfactorily for radio broadcasting and ATIS if the signals are digitized.
