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BELL SYSTEM TECHNICAL JOURNAL 



which was made in the derivation of the Q values is not valid for small tj; 

 that is, the fields for the dissipative case are not the same as those derived 

 on the basis of perfectly conducting walls. 



The expressions for the factor are rather complicated, as it depends on 

 several parameters. When a given mode is chosen, the number of param- 



eters reduces to two, 77 and R. Contour diagrams of () - vs 77 and R are 



A 



given on Figs. 9, 10, 11 and 12 for the TE Oil, TE 111, TMOll and TM 111 



Fig. 12— Coaxial resonator. TM HI mode Contour lines of Qj- 



modes. As mentioned above, the true behavior of () - for the TM Oil 



mode for small rj is not given by the above formula, so this contour diagram 

 has been left incomplete. 



Fins in a Cavity Resonator 



The suppression of extraneous modes is always an important problem 

 in cavity design. Among the many ideas advanced along these lines is the 

 use of structures internal to the cavity. 



It is well known that if a thin metallic fin or septum is introduced into a 

 cavity resonator in a manner such that it is everywhere perpendicular to 

 the £-lmes of one of the normal modes, then the field configuration and 



