A New Microwave Triode : Its Performance 

 as a Modulator and as an Amplifier 



By A. E. BOWEN* and W. W. MUMFORD 



(Manuscript Received Mar. 20, 1950) 



This paper describes a microwave circuit designed for use with the 1553- 

 416A close-spaced triode at 4000 m.c. It presents data on tubes used as amplifiers 

 and modulators and concludes with the results obtained in a multistage amplifier 

 having 90 db gain. 



Introduction 



1\ /T ICROWAVE repeaters are of two general types: those that provide 

 -^^-''amplification at the base-band or video frequency and those that 

 amplify at some radio frequency. Of the latter there are two types: those 

 that involve no change in frequency and those that do involve a change 

 in frequency, that is, the radiated frequency is different from the re- 

 ceived frequency. The Boston-New York link^ is of this last type as is 

 also the New York-Chicago link. This paper deals chiefly with a discus- 

 sion of the application of the close-spaced triode^ in a repeater of the type 

 to be used between New York and Chicago. 



A block diagram of this type of repeater appears in Fig. 1. The received 

 signal comes in at a frequency of, say, 3970 mc. It is converted to some 

 intermediate frequency, say 65 mc, in the first converter which is associated 

 with a beating oscillator operating at a frequency of 3905 mc. After ampli- 

 fication at 65 mc it is converted in the modulator back to another micro- 

 wave frequency 40 mc lower than the received signal and then it is ampli- 

 fied by the r.f. amplifier at 3930 mc and transmitted over the antenna 

 pointed toward the next repeater station. Our attention will be focussed 

 upon the performance of the close-spaced triode in the transmitting 

 modulator and in the r.f. power amplifier in this type of repeater. 



The close-spaced triode was assigned the code number 1553 during its 

 experimental stage of development and, with subsequent mechanical im- 

 provements, it became the 416A. Some of the data reported herein were 

 taken on one type, and some on the other; references to both the 1553 

 and 416A tubes will be noted throughout the text. The difference in 

 electrical performance was not significant. 



An early experimental circuit for the 1553 type tube will be described 



* Deceased. 



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