70 



BELL SYSTEM TECHNICAL JOURNAL 



The second and third harmonic products in the amphfier are illus- 

 trated in Fig. 16 which shows their relation to the fundamental for 

 different values of fundamental output. This harmonic production 

 is a good measure of the modulation performance. In this respect 



80 



70 



60 



50 



40 



30 



20 



10 



20 



FUNDAMENTAL OUTPUT 

 IN DB ABOVE I MILLIWATT 



Fig. 16 — Modulation in line amplifier. 



30 



the new amplifier is as good as or better than the push-pull amplifier 



which was used in the older system when a periodic selection of tubes 



was necessary to insure a satisfactory reduction of second harmonics. 



A gain-load characteristic of the amplifier, with respect to a single- 



