1084 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1952 



than randomly varying signal, it is felt that the comparative results will 

 apply to the random signal case as well. 



Tests were made at 150, 450 and 900 mc, at four locations of interest, 

 and with dipole and 7 db gain anteinias. Not all combinations were 

 tested, but enough to permit some interesting comparisons. The locations 

 tested were as follows: 



A: On the Long Lines building, a 27-st()i'v building in downtown 

 Manhattan. 



B: On the Graybar- Varick building, a lO-story building in downtown 

 Manhattan. 



C: On the telephone building which houses the Melrose exchange, a 

 7-story building in the center of the Bronx. 



D: On the 3-story telephone exchange building in Lynbrook, Long 

 Island. 



Table I describes the generally prevailing noise situation at these 

 locations. Higher noise was encountered occasionally at some of the 

 sites, due in at least one case to operation of elevators in the building. 

 However, these occasions were so brief and infrequent that the general 

 i)ackground of noise is considered to be a better value to use in estimating 

 systems performance. 



The trend toward lower site noise at higher frequencies, already noted 

 for mobile installations, is seen to apply to land receivers as well. 



Table I — R-F Signal Input to Receiver for 12 db Speech-to-Noise Ratio 

 (Given in db Above That Needed to Override Set Noise*) 



* Noise figures in the test receivers were 9, 12 and 12 db for 150, 450, and 

 900 mc, respectively. 



