A Study of Ultra-High-Frequency Wide-Band Propagation Characteristics

Signals reflected from buildings and other large objects introduce distortion in the received signal because of their relative time delay and phase relations. This distortion is especially evident in the form of blurred and multiple images in television reception. Data on the relative merits in this respect, of vertically and horizontally polarized waves transmitted from the Empire State Building in New York City, were obtained at the two frequency ranges of 81 to 86 megacycles and 140 to 145 megacycles. Some data using circular polarization at the lower frequency range were also obtained. The effects of indirect-path signals were indicated on recorded curves showing field strength versus frequency. The methods and equipment used to record these data at a number of representative receiving locations are briefly described. A minimum of indirect-path signal interference was found to be generally had with horizontal polarization at both signal-frequency ranges. In this respect, circular polarization was found to be slightly preferable to vertical polarization. Horizontal polarization also gave somewhat greater average field strength. Miscellaneous data and observations are described, including sample propagation-characteristic curves. In conclusion, some relations between direct- and indirect-path signals and propagation paths are discussed.