94 BELL SYSTEM TECHNICAL JOURNAL 



The symbol a is used to call attention to the fact that the in tune impedance 

 ratio is numerically equal to the voltage standing wave ratio on the input 

 line. 

 The low-level behavior of the cavity is thus defined by three equations. 



5l = 5o + 5i + 52 (4) 



T = ^^^i^^ (12) 



5i 



6o + ^2 



(13) 



High-Level Operation. The high-level performance of the cavity con- 

 taining a gas discharge can be expressed directly in terms of our original 

 definitions. Fig. 37 still applies, the transmitter admittance changing 

 to its operating value which is assumed to be 8iB at the plane AB. When 

 the gas discharge becomes conducting, the switch 5 is closed, the value of 

 the reactive power in the cavity (Po) is set by the character of the discharge 

 and the leakage power is given by 



Pr = Po52. (14) 



A constant value of Po is equivalent to a constant value of V in the figure. 

 The power dissipated in the cavity walls, the gas discharge and in the out- 

 put circuit must evidently be given by 



P, = ^ = {PP,8d"' (15) 



if F < < IJ8,B. 



Of this power an amount called the excitation power 



Pe = Podo (16) 



is lost in the cavity walls. The net loss of power in the gas discharge is 

 given by 



P„ = Px - Pr - Pe (17) 



or 



P, = (PPo5i)''- Po(5o + 52). (18) 



Since the last term is usually ver>' small compared to the first term, we may 

 write 



P, ^ (P Po5i)'/'. (19) 



