VACrr.M TIBES IVR RADAR I.I-. AMPLIITERS 



403 



parallel to the stem or "base" of the tube. The magnification in Fig. 13 

 as reproduced is about 5 3^ times. 



The heater is a conventional folded type with eight legs of coated tungsten 

 wire. The wire diameter is 0.0014 inches and the unfolded length is 3 inches. 

 The insulating coating consists of fired aluminum oxide and is about 0.0025 

 inch thick. 



The cathode is of oval cross-section with the contours of the longer sides 

 shaped to conform to the shape of the control grid. The major axis of the 



Fig. 13— Transverse section of 6.\K5 tube (53-9 times). 



cross-section of the cathode sleeve is 0.048 inch. The minor axis is 0.025 

 inch. The length of the sleeve is 0.47 inch and it is coaled over a centralized 

 section which extends 0.28 inch along its length. The coating is the usual 

 mixture of oxides of barium, calcium, and strontium. Before the tube is 

 processed, the coating thickness is about 0.002 inch, .\fter processing, it is 

 about 0.001 inch thick. 



The grids are oval-shaped and are wound with small diameter wires. 

 The control-grid and the screen-grid lateral wires are 0.001 inch diameter 

 tungsten. The suppressor-grid lateral wires are 0.002 inch diameter 

 molybdenum. The control-grid wires are gold-plated in order to minimize 

 primary emission of electrons from this grid. 



