ULTRA-HIGH-FREQUENCY POWER AMPLIFIER 



27 



coupled to the frame by means of a small rectangular single turn loop 

 mounted just beneath and quite close to the bars at the short-circuited 

 end. The second plate bridging the bars, in conjunction with the elec- 

 trostatic screen between the bars and the input coupling coil, aids in 



' 1 



Fig. 14 — Photograph of impedance measuring Lecher frame. 



1. Short-circuiting bridge carrying detector tube and detector coupling coil. 



2. Auxiliary bridge for breaking up unbalance currents flowing on the frame. 



3. Input circuit. Note electrostatic screen between frame and input coil mounted 



on end of flexible transmission line leading to driving oscillator. 



4. Clips carrying calibrating resistors. 



5. Jacks into which plugs on amplifier input circuit fit. 



eliminating any unbalance of the currents flowing in the two sides of 

 the frame. The aluminum trough surrounding the frame provides 

 sufficient shielding to render the apparatus virtually immune to the 

 operator's body capacity effects. The whole resistance measuring 



