A NEW MICROWAVE TRIODE 



541 



are the plate voltage and the beating oscillator drive. The beating os- 

 cillator power affects the low level gain only slightly but has quite an 

 effect on the gain at high power levels, that is, when the output power 

 becomes comparable with the beating oscillator power. It is seen in Fig. 

 14 that compression becomes noticeable when the output power ap- 

 proaches within ten db of the beating oscillator driving power. 



Varying the plate voltage on the modulator from 150V to 300V had 

 little effect upon the conversion gain at low levels, but more power output 



U 6 



2 4 6 8 10 12 14 16 18 2l 



OUTPUT POWER IN DBM 



Fig. 14. — Modulator compression data for tube # PS62. 



6 8 10 12 (4 



OUTPUT POWER IN DBM 



Fig. 15.— Modulator compression data for tube #PS348. 



was obtained at the higher voltages. At 15 dbm power output, very little 

 difference between 200V and 300V was observed, but at 150 V the gain 

 was down two db, as shown in Fig. 15. 



Fig. 16 shows the compression data for seven early experimental tubes, 

 used as modulators with 200V on the plate, 14 ma cathode current, and 

 200 mw of beating oscillator drive. Half of these tubes had over seven db 

 low level gain and only slight compression at power output levels of 13 

 dbm. The two poorest tubes would probably have been rejected before 

 shipment, according to present standards of production. Each of the 

 seven tubes was matched in impedance on the r.f. and i.f. inputs and also 



