RADIO BROADCAST COVERAGE OF CITY AREAS 123 



City and Washington, D. C, areas. The results of some of the earlier 

 of these surveys have already been published.^ 



Actual Distribution in New York City 



Fig. 4 presents the results of a detailed survey of the field distribu- 

 tion effected over the New York metropolitan area by Station WEAF 

 located at 463 West Street. The measurements upon which the plot 

 is based were taken in the daytime during the summer of 1925. Meas- 

 urements were taken at approximately one-mile intervals along each 

 of a series of circular paths concentric with the station, the radii of 

 which increased in steps of approximately five miles. The distribution 

 was studied in even greater detail close to the station and in locations 

 giving evidence of rapid change in field strength. Ferries were utilized 

 to extend the measurements over bodies of water. Manhattan Island 

 was circumscribed on water by measurements made upon a sight-seeing 

 boat. The land measurements were made in all cases outside of build- 

 ings at ground level. In the built-up sections of the city they were 

 taken in the middle of streets and street intersections, and in so far as 

 possible in open places. The plot is based upon over 1000 measure- 

 ments. While these measurements were taken over a considerable 

 period of time, check measurements proved conditions to have re- 

 mained quite stable and showed, in fact, little variation from measure- 

 ments made the previous year. The type of measuring apparatus 

 employed, together with certain of the results obtained in earlier 

 surveys, has already been described.^ 



This plot is actually a simplification of a more detailed one. The 

 number of contour lines has been limited to those of round figures for 

 the sake of clarity. The line marked 10,000, for example, traces the 

 locations at which that field strength was observed and beyond which 

 lower values obtained. 



This survey shows strikingly that the terrain over a city like New 

 York is anything but uniform electrically; that the variations in the 

 attenuation which the waves experience in different directions and 

 from one area to another distort the distribution pattern from that 

 which we might imagine from the familiar stone in the pool analogy. 

 It is apparent that this simple analogy will have to be amended by 

 conceiving the pool to be beset by various encumbrances causing high 

 attenuations and reflections; and, in fact, also by the presence of 



* "Distribution of Radio Waves from Broadcasting Stations over City Districts," 

 by Ralph Bown and G. D. Gillett, published in the Proceedings of the Institute of 

 Radio Engineers, August, 1924. 



^ See previous reference; also "Portable Receiving Sets for Measuring Field 

 Strengths at Broadcasting Frequencies," by Axel G. Jensen; Proceedings, I. R. E., 

 June, 1926. 



