rOUK-POLE ADMITTANCES 01- MICROWAVE TRIODES 



651 



Y and 7 are known. J22 can readily be determined by readjusting the input 

 spacing to equal the outj)ut spacing and measuring a second admittance 

 V . A'22 will be aijproximately equal to this value. There is, then, sulTicient 

 information to compute yi2 . 



^' 0.1 



a. 



O 0.09 



^ 0.08 



t|[ 0.07 



2 



^ 0.06 



Q 0.06 



1 23456789 10 11 12 



SPACING, S, OR S2,IN MILS 



Fig. 4 — Variation of passive input and output admittances with spacing. 



Two grids were used in this work. The first was a parallel wire grid of 0.3 

 mil tungsten wire wound at 1000 turns per inch. The second was also of 0.3 

 mil tungsten wound in a crisscross fashion at 550 turns per inch. Both grids 

 are shown in Fig. 3. It will be noted that the cross-lateral grid has an aper- 

 ture 220 mils in diameter. 



The values of ju and ^'22 were found to be almost purely capacitive and 

 were the same for both types of grid. These values are shown in Fig. 4. 

 A'u and y->i correspond to capacitances C'n and C22 , which agree surprisingly 

 well with the calculated capacitances between the grid and cathode, and 

 grid and plate planes, respectively. Figure 5 shows the experimentally 



