ELECTRON TUBES FOR A COAXIAL SYSTEM 



1119 



which are located at the ends of the grid proper. These then form a rigid 

 frame around which the very fine lateral wire can be spiraled without any 

 danger of having laterals out of place. It can be seen that this technique 

 produces the extremely fiat grid plane which is necessary for the desired 



6AK5 

 CONVENTIONAL 

 NOTCHED AND 

 SWAGED GRID 



404 A 



BRAZED FRAME 



GRID 



435 A 



GLAZED FRAME 



GRID 



436 A 

 AND 

 437A 

 GLAZED FRAME 

 GRID 



'^-GLAZE 



Fig. 12 — Control grids for the 408A or 6AK5, the 404A and the L3 carrier tubes. 



tube performance, and which is the real difference between these high 

 figure of merit tubes and the more conventional tubes. 



The fabrication of the 404A frame grid has been discussed in a previous 

 article.^ That article also mentioned the 418A grid which is a side rod type 



5 "Fine-Wire Type Vacuum Tube Grid," E. J. Walsh, Bell Laboratories Record, Vol. 

 XXVIII AprU 1950. 



