DISCONTINUITIES 425 



three waves must be taken into account. As current is varied, the loss param- 

 eter d varies, and this means different x's and ^''s must be computed for 

 different currents. Finally, at high currents, the space-charge parameter Q 

 must be taken into account. In all, a computation of tube behavior under a 

 variety of conditions is an extensive job. 



Fortunately, for useful tubes operating as intended, the gain is high. 

 When this is so, the gain can be calculated quite accurately by asymptotic 

 relations. Such an overall calculation of the gain of a helix-type tube with 

 distributed loss is summarized in Appendix VII. 



