1390 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1953 



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 diode. 



25 50 75 100 125 150 175 200 225 250 275 300 325 

 IMPEDANCE LEVEL IN OHMS 

 (SOURCE AND LOAD RESISTANCE EQUAL) 



Performance curves for experimental cold cathode negative resistance 



has been related to the power handUng capacity by measuring at each 

 value of source and load impedance, the maximum power output at 

 which the total harmonic distortion is 30 db below the signal. 



The noise introduced by a tube affects its usefulness as a transmission 

 element. By designing the tube so that the anode is in the Faraday dark 

 space, anode oscillations are avoided. The remaining noise is at a low 

 level, typical values being 10 decibels above the noise reference level of 

 10"'' watts. 



CONCLUSIONS 



Cold cathode glow discharge tubes can be made with stable and re- 

 producible impedance characteristics. By proper choice of anode-cathode 

 spacing and pressure of filling gas, it is possible to eliminate oscillation 

 noise associated with the anode region. By properly choosing the density 

 of filling gas and the area of a plane cathode, it is possible to obtain a 

 low positive resistance component of impedance. By proper correlation 

 of cathode geometry and filling gas density, hollow cathodes can be used 

 to obtain a negative resistance component of impedance. Bandwidth, 

 power, distortion, and noise requirements of voice frequency transmis- 



