424 



BELL SYSTEM TECHNICAL JOURNAL 



cated on each curve. This was obtained in the following manner: 

 With the transmitter turned off the noise attenuator was adjusted until 

 the introduced disturbance produced the same value of rectified current 

 as that observed when the carrier alone was applied. This determined 

 the input level from the noise generator which produced equal root- 







- 5 

 -10 



- 15 



-20 



-25 



^ -30 



_i 



ui 



g-35 



u { 



Q ' 



Z -40 



_l 



u] -45 



u 



_i 



-50 

 > 



^-55 



_i 



UJ 



a. 



-60 



-65 



-70 



-75 



-80 



-85 



6 8 10 12 14 16 



FEEDBACN IN DECIBELS 



18 20 22 24 



Fig. 11 — Effect of feedback upon receiver distortion. Modulation held to a constant 



value of ± 7 kilocycles. 



mean-square values of intermediate-frequency carrier and disturbance. 

 Since at very low inputs from the noise generator the net intermediate- 

 frequency disturbance was determined partly by tube noise generated 

 within the receiver, a curve of output noise without feedback versus 



