Comparison of Mobile Radio Transmission 

 at 150, 450, 900, and 3700 Mc 



By W. RAE YOUNG, JR. 



(Manuscript received August 22, 1952) 



Based on a series of experiments, a comparison is made of the transmission 

 performance of 150, 450, 900, and 3700 mc in a mobile radiotelephone type 

 of service. This comparison indicates that 450 mc is superior transmission- 

 wise to the presently used 150-mc hand in urban and suburban areas. In 

 fact a broad optimum in performance falls in the neighborhood of 500 mc 

 It is concluded that this range of frequencies woidd be well suited for pro- 

 viding coverage to meet the large scale needs which are anticipated in and 

 around metropolitan areas. Although higher frequencies are less desirable, 

 the tests indicate that 900 mc is somewhat to be favored over 150 mcfrom a 

 transmission standpoint if full use is made of the possible antenna gain. 

 Above this frequency, transmission performance falls off even assuming the 

 ma.umum practical antenna gain. Transmission at 3700 mc suffers an 

 additional impairment in that the fluctuations in received carrier level occur 

 at an audible rate as the mobile unit moves at normal speeds. It is con- 

 cluded that while transmission above roughly 1000 mc for these services is 

 not impossible, it woidd be decidedly more difficidt to employ these frequen- 

 cies satisfactorily. 



INTRODUCTION 



From the beginning of mobile radiotelephone services offered by the 

 Telephone Companies, both "general" and "private-line" types, it has 

 been apparent that the number of channel frequencies then allocated for 

 these uses would not be sufficient to meet the service needs in the 

 near future. 



The bulk of these needs ^vill be for service in urban and suburban 

 areas, where business activities are concentrated. These areas are now 

 served on a few individual FM channels in the vicinity of 150 mc. 

 However, a larger number of channels, needed to meet anticipated de- 

 mands and to develop a more efficient system, are not to be found in the 



1068 



