A Radio Field Strength Survey of Philadelphia

Measurements of the strength of the electromagnetic waves broadcast by station WFI were taken at representative locations throughout the city of Philadelphia and its environs. In the method used, measurements of the antenna loop resistance were used as a guide in determining when interference was sufficient to cause the rejection of a particular field strength reading. Lines of equal field strength were plotted on a map of the territory; these showed the location of several shadows and of one area in which the field strength was considerably higher than in the surrounding neighborhood. Conditions throughout the city remained virtually unchanged during the two years of the survey, with the exception of a considerable new shadow cast by a large building recently erected near the broadcasting station.