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BELL SYSTEM TECHNICAL JOURNAL 



criminate against a component of higher frequency than the one being 

 measured, it is advantageous to use the voltage across the condenser, 

 whereas if the interfering component is of lower frequency, the voltage 

 across the inductance should be used. It is therefoi'e desirable to make 



6 6 6 



Fig. 2 — ^High frequency amplifier unit No. 1 of heterodyne current analyzer 



provision by means of a switching arrangement whereby the voltage 

 may be applied from either the inductance or the capacity depending 

 upon the discrimination desired. With the coils and condensers used 

 the voltage across the condenser at resonance is over a hundred times 

 that across the coupling resistance. 



TO MODULATOR 





1 



Fig. 3 — High frequency ampHfier unit No. 2 of heterodyne current analyzer 



The first tube of each unit serves as a voltage amplifier. This works 

 into a high resistance between the grid and filament of the power tube. 



