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BELL SYSTEM TECHNICAL JOURNAL 



500-cycle component, and the upper trace the 750-cycle component. 

 The upper and lower traces have their zero hues at the edges of the 

 strip. This record was made at Riverhead, L. I., April 30, 1925, at 

 3 :33 a.m. Strip 2 is a section of a record made a few minutes later when 

 an unstabilized carrier was being used. 



The gain in the audio amplifiers connected to the outputs of the 

 filters was adjusted to give nearly uniform transmission through the 



Time 





^ 



Fig. 44 — Slow record made with system diagrammed in Fig. 43. Contrasting the 

 distortion of detected tone transmitted by stabilized and unstabilized carrier frequency 



receiving and recording apparatus for the frequencies recorded. Hence 

 in these records the relative amplitudes of the fundamental and 

 harmonics of the signal are directly comparable. 



Strips 3, 4 and 5 in Fig. 44 are taken from a record made for the 

 purpose of obtaining a comparison of the wave form distortion sus- 

 tained by the detected audio signal transmitted by the normal trans- 

 mitter with frequency modulation present and by a stable frequency 

 transmitter. In each strip the lower trace is the whole tone from the 

 output of the radio receiver, the middle trace the second harmonic 

 (500 cycles) and the upper trace the third harmonic (750 cycles). 

 Strip 3 and half of Strip 4 give the record obtained when the normal 

 transmitter was used, and the remainder is the record obtained when 

 the modified transmitter was used. There was a few minutes' difference 

 in time between the ending of one transmitting condition to the begin- 

 ning of the next during which the master oscillator control was switched 



