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BELL SYSTEM TECHNICAL JOURNAL 



on the single-sideband system was 10 db higher, and when the signal- 

 to-noise ratio on the double-sideband system was 40 db the average 

 signal-to-noise ratio on the single-sideband system was 5 db higher. 

 The lesser improvement with the single-sideband system for the 

 higher signal-to-noise ratios was probably due to limitations in the 

 maximum signal-to-noise ratio obtainable from the transmitting 

 equipment. 



Figures 10 and 11 are plots of the average signal-to-noise ratio 

 versus field for the single and double-sideband systems. Only double- 

 sideband fields were measured and the average single-sideband 

 signal-to-noise ratios are plotted against the average of the preceding 



60 



O 30 



'A 10 



-10 



10 



20 



30 



40 



50 



DOUBLE SIDEBAND FIELD STRENGTH IN DECIBELS ABOVE 



l/JV 



Fig. 11 — Plot of signal-to-noise ratios on double sideband vs. field strength. 



and succeeding double-sideband measurements. The crosses shown 

 on the curve are the averages of all signal-to-noise ratios in 1 db 

 intervals of field and the dots shown are averages of all fields obtained 

 when the signal-to-noise ratio lay within 1 db intervals. The dotted 

 lines represent the ma.ximum signal-to-noise ratio which the receivers 

 will give for various values of field. It is seen that on the average the 

 set-noise was not the limiting factor determining the signal-to-noise 

 ratios obtained. 



