602 



BELL SYSTEM TECHNICAL JOURNAL 



OSCILLATOR 

 TUBE 



TUNED 



CIRCUIT 



AND 180 



PHASE SHIFT 



NETWORK 



±90° 



PHASE SHIFT 



NETWORK 



REACTANCE 

 TUBE 



MODULATING 

 INPUT 



Fig. 1 — Simplified schematic of conventional reactance tube modulated oscillator. 



OSCILLATOR 

 TUBE 



90° 



PHASE SHIFT 



NETWORK 



90° 



PHASE SHIFT 



NETWORK 



REACTANCE 

 TUBE 



MODULATING 

 INPUT 



Fig. 2 — Simplified schematic of phase shift reactance tube modulated oscillator. 



OSCILLATOR 

 TUBE 



+ 90" 



PHASE SHIFT 



NETWORK 



t90° 



PHASE SHIFT 



NETWORK 



REACTANCE 

 TUBE 



MODULATING 

 INPUT 



TUBE CONNECTION 



NETWORKS 



OSCILLATION FREQ. 



LEADING (+90°) LAGGING (-90°] LEADING (+90°) 



DECREASES 



INCREASES 



B 



DECREASES 



LAGGING (-90°) 



INCREASES 



Fig. 3 — Direction of frequency deviation for increasing Gm of reactance tube. 



