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BELL SYSTEM TECHNICAL JOURNAL 



tenth round trip, but the superiority of the 416A amplifier is clearly 

 shown in the hundredth round trip. 



Both amplifiers were operating at low levels, and the pulse was an am- 

 plitude modulated one. Since these are not the conditions under which 

 our microwave radio relay circuits operate, conclusions should not be 

 drawn about how many repeater stations can now be put in tandem. The 



Fig. 23. — An assembled three-stage microwave amplifier. 



test merely indicates that an improvement has been made, thus corro- 

 borating the evidence obtained by other tests. 



Still further improvement has been made since loop testing the model 

 ten amplifier. A three stage 416A amplifier (see Fig. 23) using model 

 eleven circuits had comparable gain, 23 db, but a bandwidth of 50 mc to 

 points 0.1 db down. These data again are for low level operation, but it 

 is reasonable that half a watt might be expected from four such stages 

 with comparable gain and slightly narrower bandwidth, surely 30 mc. 



