TRAVELING WAVE TUBE FOR 6,000-MC RADIO RELAY 1345 



(/ = 1. The region for which d > 1 was considered as a severed helix 



region with 6-db discontinuity loss. Calculations using this procedure 



gave total gains for the TWT within a couple of db of the first method. 



The remaining steps in calculating the gain of the TWT are therefore: 



(8) The quantity a is determined from the slope of the dotted lines 

 in Fig. 48. 



(9) The length of helix, 4 in the attenuator for which x > is 

 determined by using Fig. 48. 



(10) The total attenuation L, in the section of the attenuator effective 

 in producing gain is calculated. 



(11) The initial loss parameter A is obtained from Fig. 94 of Pierce J 



(12) The gain is calculated from 



Gain = A -6dh +aL + BCNi (3.5 + /«) 



where the six db is the discontinuity loss in the attenuator section and the 

 3.5 inches is the length of loss free helix. 



Glossary of Symbols 



a loss factor from Pierce^ 



A discontinuity loss parameter at input of helix from Pierce^ 



B magnetic flux density or the space charge parameter from Pierce 



Bb Brillouin flux density for a beam entirely filling the helix 



C gain parameter from Pierce^ 



a helix radius 



b beam radius 



d loss parameter from Pierce'^ 



/ frequency 



Ik cathode current 



la accelerator current 



Ih helix current 



Ic collector current 



k 2ir/Xo where Xo is the free space wavelength 



fe length of helix attenuator in which gain is possible 



L loss in the part of the attenuator section which is capable of pro- 

 ducing gain. 



A'' number of wavelengths in TWT 



Ni number of wavelengths on the helix per inch 



QC space charge parameter from Pierce^ 



Ta anode radius of curvature of gun 



Tc cathode radius of curvature of gun 



Tmin minimum beam radius from Pierce'" 



