ADMITTANCES OF I'ARALLEL-PLANE ELECTRON TUBES 



623 



Now, assume that the right-liand transmission line is removed and that 

 the diode gap is connected at the transformer terminals Xo . The normalized 

 admittance referred to the point yo on the input line can be measured by a 

 simple standing wave measurement. Represent this admittance by F^y . 



Fig. 4 — Coaxial tester. 



Let the unknown diode admittance be represented by F^ . Yx is then given 

 by the following relation: 



^ [Yu-o + jp\ (-i) 



Fx = 



Z 



OxW 



Hence, having determined yo , it is only necessary to measure the slope m 

 and the intercept p on the cot-cot curve in order to relate Y:, to Y,,.g . The 

 characteristic impedance of the output line Zqx used in obtaining the cot-cot 

 plot must also be known. Since a coaxial is used for this line, its charac- 

 teristic impedance is easily calculated. 



If no losses were associated with the transformer or the parts of the diode 

 external to the actual cathode-anode region, such as the metal vacuum 



