This study investigates the propagation links of two Digital Terrestrial Television Broadcast Stations (DTTBS) in the tropical rain forest (Akure) and Sahel Savannah (Katsina) cities of Nigeria. Digital field strength values of the base stations were measured at intervals of 1km along some selected routes around the stations using a digital signal strength meter. A GPS receiver was used to monitor the line of sight with the station as reference and to log the geographic coordinates and heights of data points. Data were collected in some wet and dry months for a period of two years. Result shows that the Received Signal Strength (RSS) decayed inversely with distance for all the routes and seasons. However, there were few exceptions where some farther trans–receiver distances recorded higher signal strength compared to nearer points contrary to theoretical expectation. This can be attributed to the influences of terrain particularly the elevation above sea level of the study areas and some other factors such as meteorological parameters and surface radio refractivity. Signals were generally enhanced when receiver antenna height of 3.0 m was used compared to the values obtained when using the receiver antenna height of 1.5 m. Signal strength enhancement attributed to higher receiver antenna was more pronounced during the wet season compared to the dry season in Akure. However, the enhancement was relatively consistent for both seasons in Katsina. The average distances in which the signal strength decays to about half of its initial value in Akure and Katsina were 8.0 and 10.0 km (LOS) respectively. From the statistical analysis of data, mean values of elevation over the study areas were 357.07 m and 523.97 m in Akure and Katsina respectively. In addition, mean values of 0.53 and 0.80 positive correlation coefficients were obtained between RSS and elevation above sea level of study locations in Akure and Katsina respectively. Results further revealed that digital terrestrial television signal suffers lesser attenuation in the Sahel Savannah region compared to the tropical rainforest zone. The overall findings of this work will be useful for planning DTT links and network over the study areas.
Key Words: Digital Terrestrial Television, Propagation links, Elevation and NTA-Star times