Validation and Modification of the Stanford University Interim Path Loss Model for Very High Frequency Propagation in Calabar, Nigeria

This study focuses on the validation and modification of the Stanford University Interim (SUI) path loss model for Frequency Modulated (FM) signal propagation at 105.5 MHz within the Calabar environment. Empirical measurements of received signal strength were taken across twelve geographically diverse locations in Calabar, using a digital spectrum analyzer and GPS receiver to capture signal and positional data. The standard SUI model was applied to the collected data, and significant deviations were observed between the predicted and measured path loss values. A correction factor of 42.50 dB was subsequently introduced to account for the discrepancies. The modified SUI model yielded a Root Mean Square Error (RMSE) of 11.65 dB, indicating improved prediction accuracy compared to the unmodified version. However, this error margin still exceeds the International Telecommunication Union (ITU) threshold of 6 dB for acceptable path loss prediction accuracy. The findings demonstrate that while the modified SUI model performs better than the original, it remains insufficiently accurate for FM signal prediction in Calabar. The study highlights the necessity of developing or further refining propagation models based on local environmental conditions. It contributes to the broader discourse on region-specific path loss modelling and provides valuable insights for RF engineers, broadcasters, and researchers concerned with network planning and optimisation in Calabar.