March 1981 | NTIA Technical Report TR-81-68
Television Field Strength and Home Receiving System Gain Measurements in Northern IIIinois
Raymond D. Jennings
Abstract: Throughout an area between Chicago and Peoria, Illinois, approximately 50 measurement locations were selected. At each location measurements were made, typically, for two VHF television broadcasts from Chicago and three UHF television broadcasts from either Chicago or Peoria. Measurements were made using a standard antenna erected on the measurement van to the same height as the home antenna. Cumulative distributions of these measurements were produced from which the median electric field strengths were computed and plotted at each measured Chicago broadcast frequency, as a function of distance from the broadcast (transmitting) antenna. The least squares, linear regression line for each set of data is shown. Also shown are field strengths required by FCC Regulations for Grades A and B Service and the coverage ranges at which each Grade of Service is realized scaled from contours published in the Television Factbook and as computed using an automated model named COVERAGE which uses a modified version of the FCC propagation loss curves (discussed in Appendix B). Measurements of received signal level also were made using each home antenna system. Using the two types of measured data, cumulative distributions of sample home antenna system gain are presented for each measurement frequency and location in Appendix A. Median values from these cumulative distributions have been chosen as estimates of gain for the home antenna systems. It is concluded that systems using single-function antennas typically have significantly higher system gain than systems incorporating VHF/UHF combination antennas. Statistical results (median and interdecile values) from the measured data provide the basis for a generalized model for VHF and UHF television receiving antenna system gain. Though home antenna systems can be installed to provide excellent performance, the measurements show that in-service antenna system performance is 0.4 dB to 12.5 dB less than has been assumed. All the measured data were obtained and are retained in digital form on magnetic tape.
Keywords: antenna system gain; electric field strength; gain model; grade of service; measurements; statistical analyses; UHF television; VHF television
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