ANALYSIS OF RADIO WAVES PROPAGATION FOR FM BROADCASTING STATION (A CASE STUDY OF OSUN STATE BROADCASTING CORPORATION OSOGBO)

Abstract

FM broadcast coverage in developing urban environments is frequently affected by terrain, building density, obstruction and multipath, yet station-level propagation data remain limited. This study investigated radio-wave signal-strength variation and propagation characteristics of the Osun State Broadcasting Corporation (OSBC) FM signal in Osogbo, Osun State, Nigeria, operating at 104.5 MHz, with a transmitting power of 100 W and a mast height of 340 m. An experimental quantitative design was adopted, with the coverage area divided into four routes: OSBC–Air Force Base–Ibokun Road (rural), OSBC–Ilesa Garage–Osun River (riverine/urban), OSBC–Stadium–Ring Road (densely built-up), and OSBC–Oja Oba–Isale Aro–Ola Iya (mixed urban/semi-urban). Measurements were taken at 1-km intervals from 1 to 6 km during daytime and evening periods over three weeks using an Agilent N9342C spectrum analyser and a Diamond RH799 omnidirectional antenna at 1.5 m. Signal strength declined across all routes, with net reductions of 76%, 70%, 62% and 90% for Routes 1–4, respectively. Route 4 exhibited the greatest attenuation variability (SD = 21.54; range = 64.35), whereas Route 2 recorded the highest mean signal strength (39.31) and lowest variability (SD = 15.57; variance = 242.57). Predicted eHata path loss increased with distance, ranging from 61.10 to 85.72. Elevation showed no consistent relationship with signal strength, indicating the influence of local propagation conditions. Signal strength fell below the reported minimum acceptable level of 40 within 2–3 km on all routes. The findings highlight the need for optimized antenna siting, appropriate power planning and mitigation of multipath and shadowing effects.