528 



BELL SYSTEM TECHNICAL JOURNAL 



The calculation is based on the following assumptions (Fig. A2-2): 

 1. The output cavity has inner diameter .180", outer .850", conse>j 

 quently a characteristic admittance Go : 



Go = 7250/log J = 10,710 micromhos 



(A2-1] 



2. The gap capacitance is that of a parallel plate condenser of .180" 

 diameter and .012" spacing, namely 



C22 = tnA/d= 0.477 mm/ (A2-2) 



3. The effect of the glass vacuum envelope is neglected for simplicity. 



/ OOij'i^ 



E LINES 



Fig. A2-2. — Output cavity dimensions. A, B are concentric cylindrical portions. Actual 

 lines of electric force are partly dotted into sketch. 



(Consequently the length 1 of the line is given by the well-known tuning 

 relation 



C0C22 = Go cot 6 — Gq cot 



0)1 



(A2-3) 



The distributed capacitance of the line is determined from the formulas 

 (3) of the text, which in this case reduces to the following: 



?^ I 1 4- '^L^ 1 

 2~V "^"gT/ 



-CV2 = -2-11 + 



o;C22 



(A2-4) 



The cavity distributed capacitance is thus comparatively easy to calcu- 

 late at high frequencies because of the simplicity of the geometry. At low 

 frequencies the computation of the distributed capacity of a coil is no 



