MICROWAVE REPEATER RESEARCH 



245 



the antenna. The variations produced in both the ampHtude and delay 

 of the signal currents are shown by the curves in the figure where relative 

 change in the characteristics in question are shown as ordinates and values 



of the quantity — - are shown as abscissas. 



It will be seen from these curves that the amount of variation over a given 

 band is a function of the line length. With short Imes the amount of varia- 

 tion over a band 10 mc wide can be kept very small, but with lines about 

 150 feet in length there may be three or four full cycles of variations in 

 a band 10 megacycles wide. Table A gives some typical values of the varia- 

 tions. Values are given for those degrees of mismatch which would produce 

 standing wave ratios of 1, 1.4 and 2 db at the junctions. It will be seen that 

 for lines between 100 and 200 feet in length the variations in some cases are 

 greater than the limits achieved in the multistage amplifiers and other com- 



Table a 



ponents of the system. Furthermore, it is usually impractical to compensate 

 or tune out these variations because they are functions of the electrical 

 length of the transmission lines and subject to change with temperature, 

 frequency, and other small mechanical and electrical changes. It would 

 appear that with present techniques this may be one of the most serious 

 sources of distortion in a long relay system. 



VII. Conclusion 



Various phases of our work on microwave repeater circuits have been dis- 

 cussed. Such a circuit, made up of several repeaters as described in the 

 last section, may be looked upon as a four-terminal network having speci- 

 fied ampHtude and delay characteristics and should be suitable for the trans- 

 mission of any signals for which the characteristics are adequate whether 

 they be television signals or those of one of the various forms of multi- 

 plex telephony. It is outside the scope of this paper to discuss the uses to 

 which such a repeater circuit might be put or the terminal equipment that 

 any particular service might require. 



The New York-Boston repeater circuit has been built to provide the ex- 

 perimental field trials necessary to answer many remaining questions which 



