. The Bell System technical journal . 0 REACTANCE TUBE GRID VOLTS Fig. 7—Performance curves of typical LC reactance tube modulated phase shiftoscillator. simplified form is shown in Fig. 1. The input and output of a vacuumtube amplifier are connected together by a tuned circuit and feedbacknetwork which introduces 180° phase shift at the undeviated frequency Fq . Ill ASK Slllir OSCILLATORS 605 2600240022002000 O ^ 1400 JIZZZZ~Z. zzz~zzzz: o> \ o 8-7 -6 -5 -4 -3REACTANCE TUBE GRID VOLTS Fig. 8—Performance curves of typical RC reactance tulie modulated phase shiftoscillator.
. The Bell System technical journal . 0 REACTANCE TUBE GRID VOLTS Fig. 7—Performance curves of typical LC reactance tube modulated phase shiftoscillator. simplified form is shown in Fig. 1. The input and output of a vacuumtube amplifier are connected together by a tuned circuit and feedbacknetwork which introduces 180° phase shift at the undeviated frequency Fq . Ill ASK Slllir OSCILLATORS 605 2600240022002000 O ^ 1400 JIZZZZ~Z. zzz~zzzz: o> \ o 8-7 -6 -5 -4 -3REACTANCE TUBE GRID VOLTS Fig. 8—Performance curves of typical RC reactance tulie modulated phase shiftoscillator. IU5 / / 95 / ^ / 90 / z ■ —- ^ ^ ■8 -7 -6 -5 -4 -3 REACTANCE TUBE GRID VOLTS Fig. 9—Performance curves of typical transmission line reactance tul)e moduialeioscillator. 606 BELL SYSTEM TECHNICAL JOURNAL An auxiliary path contains the reactance tube fed from a 90° phase shiftnetwork connected as shown. The direction of frequency deviation is deter-mined by the sign of the 90° phase shift. The amount of the deviation is. Fig. 10—Construction of transmission line reactance tube modulated oscillator,(a) Tube side, (b) Line side. determined by the transconductance variation of the reactance tube, bythe impedance across which the reactance tube is connected and by theloss in the 90° phase shift network. The linearity is a function of all of thesefactors. In general the frequency deviation may be increased by increasing PHASE SHIFT OSCILLATORS 607 the L/C ratio in the oscillator tuned circuit, but only at the expense offrequency stability. A simplified schematic of the reactance tube modulated phase shiftoscillator is shown in Fig. 2. The mathematical theory of operation is anal-ogous to that of the conventional reactance tube modulated oscillator, andthe same methods of analysis may be applied. The 90° phase shift networkrequired in the reactance tube grid circuit is a portion of the feedback net-work and provides half of the 180° phase shift required for oscilla
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