SPARK GAP SWITCHES FOR RADAR 



571 



single gap breakdown voltage. In this case the switcii voltage may be 

 increased to a value three times that of the breakdown of one gap before the 

 three gaps can break down without addition of trigger. Thus the ratio of 

 maximum to minimum operating voltage is three to one. Ideally this 

 ratio may be increased by the addition of more gaps. 



J^ 



(a) 



PULSE 

 FORMING 

 NETWORK 



LOAD 



FROM 



CHARGING 



CHOKE 



FROM 



TRIGGER 



CIRCUIT 



JT 



w 



PULSE 

 FORMING 

 NETWORK 



(b) 



Fig. 5 — Line modulator circuit (a) using two fi.xed gaps as switch, (h) using three fixed 

 gaps as switch. 



The operating characteristics of actual gaps do not conform exactly to this 

 simple picture as we shall see later. This is because the breakdown volt- 

 age of a gap is not singly valued but depends on a variety of conditions such 

 as rate of rise of applied voltage, pulsing rate, and the energy of the pulse, as 

 well as the type of gap employed. However, we may regard it as a qualita- 

 tively correct picture of the operating characteristics of series gaps. 



A more complete description of operating characteristics will be given in a 



