ADMITTANCES OF PARALLEL-PLANE ELECTRON TUBES 627 



perceptible change in the waveguide standing wave ratio. Under such 

 conditions the electrons experienced a large retarding field at tlie cathode 

 and did not emerge an appreciable distance into the cathode-anode region. 

 Any resistance measured at tiiis time was due to the series loss and was not 



0.5 1.0 



ANODE VOLTAGE, Vq 



Fig. 7— Effect of heater voltage upon diode conductance. 



produced electronically. The diode series resistances varied from about 1.3 

 to 5.0 ohms with an average value around 3 ohms. 



Figure 6 shows the results of admittance measurements of a diode. As 

 expected, the high-frequency conductance is considerably greater than the 

 low-freqiiency value go . In fact g is seen to have a value of several thousand 

 micromhos when the negative bias of the tube is such that no perceptible 

 anode current flows. The susceptance b for large negative anode potentials 



