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BELL SYSTEM TECHNICAL JOURNAL 



the average potential of the horizontal plates of the indicator is maintained 

 at a value determined by the d-c plate potentials and, as indicated pre- 

 viously, this same potential should be applied to the second anode of the 

 cathode-ray tube to avoid defocussing effects. Another variation of a 

 phase inverter amplifier which is commonly employed in radar sweep cir- 

 cuits is illustrated schematically in Fig. 54b. In this instance, a common 

 cathode impedance is employed to accomplish similar excitation of the 

 balanced output tubes. If one grid is excited the plate current flow of this 



It 



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Fig. 55. — -Voltage-current-time relationships for magnetic deflection structures. 



tube through the cathode resistance serves to excite the second tube and a 

 balanced output sweep signal voltage will result. The values of the plate 

 resistors in this form of circuit are of unequal values and must be adjusted 

 to produce the desired balanced output. The additional control illustrated 

 in the grid circuit of V^ may be employed to serve as a d-c positioning con- 

 trol. 



The sweep amplifier design considerations involved for the magnetic 

 deflection type of cathode-ray tube radar indicator are somewhat more 

 involved, due primarily to the character of the amplifier load impedance. 

 In the case of magnetic deflection the fuial flux density, and accordingly the 

 sweep current through the deflection coil, is required to be proportional to 



