FM RADIO SIGNAL STRENGTH MODELING AND PREDICTION IN BLUE RIDGE AND VALLEY & RIDGE PHYSIOGRAPHIC PROVINCES, U.S.A

Radio wave propagation modeling is used to predict the strength of a transmitter’s signal at a certain distance. It is performed for commercial radio broadcasting stations, television stations, as well as cellular and wireless companies. Many factors can influence a radio signal in a terrestrial environment, often in a negative way, that reduces signal strength. There are many examples in literature that document radio propagation studies across the spectrum, however, there is little information documenting radio propagation modeling across two distinct geographical areas, in which results were analyzed.

The objectives to this study were to develop FM radio propagation model outputs using Radio Mobile software, then to compare model outputs with field data using a spectrum analyzer. Additionally, statistical analyses were performed to see how different factors affect signal strength. Initial results showed that Radio Mobile’s signal strength predictions across both geographic areas were more generous than what was discovered in the field. Radio Mobile was more accurate in its signal strength predictions at locations farther away from each transmitter rather than locations closer to the transmitter. The factors found to have the most influence on a radio signal were transmitter power, elevation of transmitter, transmitter azimuth, path loss, elevation angle, and distance between transmitter and receiver, according to Shapiro and Wilks test of normality. The strongest correlations among factors were test site elevation with transmitter azimuth; elevation angle with transmitter elevation; and path loss with distance. These correlations were observed in the entire study area as well as in each of the physiographic provinces separately. As a final result, model equations were formed which can be used for signal strength prediction (in dBm) of any FM transmitter so long as the variables of transmitter power, transmitter elevation, elevation angle, and distance between transmitter and receiver are known. The adjusted R2 value (confidence level) of the model equation for the study area was found to be 0.52. For Valley and Ridge province, the confidence level was 0.60, and for Blue Ridge province, the confidence level was 0.43.