Ultra-Short-Wave Propagation : Mobile Urban Transmission 



Characteristics * 



By C. R. BURROWS, L. E. HUNT and A. DECINO 



This paper, a sequel to one entitled " UItra-Short-\Vave Propagation," 

 deals with transmission in urban areas. The experimental data were 

 obtained in the City of Boston on a frequency of 34.6 megacycles per 

 second by means of a specially equipped motor car for carrying the receiver 

 while the transmitter was fixed or vice versa. 



Mass plots of these data show that the mean field strength varies in- 

 versely as the square of the path length which is the same variation as 

 would be expected for level terrain in the absence of buildings. The same 

 data are presented in the form of field strength contour maps. 



These data are interpreted on the basis of the same physical picture 

 which has been established for open country. The present data preclude 

 interpretation upon the basis employed by earlier investigators of ultra- 

 short-wave propagation through urban areas. 



It is concluded that ultra-short-wave transmission in urban territory 

 may be interpreted on the basis of transmission over level land plus the 

 wave interference patterns caused by reflections from the buildings and an 

 additional attenuation which on the average is independent of the length 

 of the transmission path. Also, if the theoretical formula for the propaga- 

 tion of ultra-short waves over level terrain is used to calculate the received 

 field in urban territory, and the height of the fixed antenna is measured 

 from the local roof level instead of from the ground, these data indicate 

 that the field strength so calculated would be near to the mean of the actual 

 received field strengths in urban territory. 



Introduction 



THIS paper is a sequel to an earlier paper, "Ultra-Short-Wave 

 Propagation," ^ which dealt mainly with transmission across 

 open country. In the present paper the research has been extended to 

 include transmission within a built-up region. Additional problems of 

 transmission within urban areas that result from man-made inter- 

 ferences, such as the noise produced by automobile ignition systems, 

 have been investigated. 



A specially equipped motor car was used as a mobile laboratory for 

 most of this work both because of its convenience as. a means of ob- 

 taining transmission data and because of the importance of mobile 

 communication itself. 



This paper describes general characteristics and quantitative meas- 

 urements of the received signal on 34.6 megacycles. Transmission 



* Published in Electrical Engineering, January, 1935. 



1 J. C. Schelleng, C. R. Burrows and E. B. Ferrell, "Ultra-Short-Wave Propaga- 

 tion, Proc. I. R. E., Vol. 21, pp. 427-463, March, 1933 and Bell Sys. Tech. Jour., Vol. 

 12, pp. 125-161, April, 1933. 



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