GAS-DISCHARGE TRAhSM IT-RECEIVE SWITCH 



67 



The way in which the spike energy varies with pressure of the gas in the 

 TR tube is illustrated in Fig. 20. These data were obtained on the 724B 

 tube structure. Other factors, yet to be discussed, prevent the use of the 

 exact optimum pressure as determined on the basis of the spike energy 

 only. 



The Flat. The more or less flat portion of the leakage power is in reahty 

 the result of two different mechanisms of energy transfer, one of which is 

 reasonably independent of the transmitter power level. It is this portion 

 only with which we will now be concerned. This flat power is critically 

 dependent on the chemical constitution and pressure of the gas within the 

 TR tube. It can be thought of as being the power transmitted by the TR 



2 5 10 20 



HYDROGEN PRESSURE IN MM. OF MERCURY 



Fig. 21 — Experimental curves showing the relationship between flat leakage power and gas 

 pressure, taken with a c-w oscillator 



box by virtue of the fact that the voltage drop across the gas discharge is not 

 zero. The constancy of the flat power in spite of variations in the trans- 

 mitter power level is presumably related to the similar phenomenon of a 

 nearly constant voltage drop across a d-c gas discharge independent of the 

 discharge current. Because of this constancy, the gas discharge parameter 

 A, shown in Fig. 15, can be assumed to be a constant more-or-less inde- 

 pendent of the transmitter power level. Reasonable values of /'o for cavity 

 design purposes are 20 volt-amperes for the 721 A tube and 10 volt-amperes 

 for the 724B tube. Corresponding values of the Qq parameters needed in 

 interpreting Fig. 15 are 2500 for the 721A tube and 1500 for the 724B tube. 

 Using these values the flat leakage power for a TR box using a 721 A tube 



