The Use of Field-Intensity Measurements for Commercial-Coverage Evaluation

This paper traces progress in developing methods of defining the commercial-coverage area of broadcast stations by means of field-intensity measurements made by the staff of a service known as Radio Coverage Reports. The initial undertaking of the service was at field survey covering the northeastern states to determine more suitable standards for contour surveys than the accepted 10.0, 2.0, and 0.5 millivolts per meter for urban, suburban, and rural service, respectively. The investigation proved that no fixed set of standard values would serve the purposes of commercial evaluation or would be productive of coverage maps tending to coincide with the disclosures of listener station-utilization findings. The methods used by Radio Coverage Reports in reporting "complete spectrum observations," defining day and night physical delivery of every audible station in cities of over 25,000 population are examined and the resulting concept of a "prevailing standard" based on available service is explained. A correlation of an extensive co-incidental listener survey made by C. E. Hooper, Inc., with Radio Coverage Reports findings shows that the listening audience varies in accordance with the prevailing standard of physical delivery. The possibilities of mapping station and network coverage in accordance with an accurately determined prevailing service are then explored.