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PROCEEDINGS OF THE AMERICAN ACADEMY. 



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that the discharge takes place for some time at one definite point on 

 the aluminum, this confinement of the discharge to one place resulting 

 possibly from the protecting oxide film over the rest of the surface. 



Part III. 



Practical Considerations and Applications. 



(1) Practical Considerations. 



From a practical point of view interest centers on the question of 

 the amount of power obtainable from the system. The gap is not 



a high-power generator of 

 electrical oscillations ; its 

 advantages lie in simplicity 

 and regularity. The con- 

 ditions for maximum power 

 were considered in Part I, 

 and it was seen that the 

 maximum power efficiently 

 obtained from one gap at 

 100 meters wave length is 

 about 40 to 45 watts. It 

 is probable, although no 

 extensive tests have yet 

 been made, that the power 

 obtainable is greater at longer, wave lengths. 



If greater power is required, gaps can profitably be operated in 

 series. Two gaps work perfectly and three gaps well on 500 volts, 

 with much increased power output. Four gaps were satisfactorily run 

 on 1000 volts, but in general there is a slight sacrifice of regularity of 

 operation as the number of gaps in series is increased. 



The amount of power obtained, when gaps are operated in series 

 with a definite supply current, is not directly proportional to the num- 

 ber of gaps. When two gaps are operated in series, the power output 

 is almost twice that from one gap. When more gaps are connected in 

 series, the gain in power is much less, the greater the number of gaps 

 the less the gain in power output. 



The average voltage across one gap ranges from 90 to 150, but is, 

 under most conditions, about 100. As the number of gaps in series is 

 increased, the current being constant, the voltage across the series 

 is practically proportional to the number of gaps. 



The efficiency of the system, when gaps are operated in series, 

 decreases as the number of gaps is increased. 



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3 



GAP5 IN SERIES 



Figure 19. Gaps in Series. 



