. Operation of the modulator tube in radio telephone sets . the diagram of Fig. i, a source of reactivecomponent to the load on the modulator tube has been deriveddue to the reactance of apparatus in the modulator unit. Simi-larly a second source of reactance load exists in the generatingunit. Thus in the diagram,Fig. 5,condenser Cb is required to beof low reactance for the radio frequency current, but of high react-ance for audio currents. If the ratio of the radio frequency tothe audio frequency is low, it may not be possible to satisfy boththese requirements. The characteristics of the gene
. Operation of the modulator tube in radio telephone sets . the diagram of Fig. i, a source of reactivecomponent to the load on the modulator tube has been deriveddue to the reactance of apparatus in the modulator unit. Simi-larly a second source of reactance load exists in the generatingunit. Thus in the diagram,Fig. 5,condenser Cb is required to beof low reactance for the radio frequency current, but of high react-ance for audio currents. If the ratio of the radio frequency tothe audio frequency is low, it may not be possible to satisfy boththese requirements. The characteristics of the generating systemshown in Fig. 2 were for very low audio frequencies, such that PuTtngton] Modulator Tube in Radio Telephone Sets 391 reactive effects due to the condenser are negligible. Kven with thecondenser present, and with actual operating audio frequencies, thecurrent ib may be interpreted as the average space current to theoscillator tubes dtuing a radio cycle, corresponding to the averageplate voltage e^. However, to produce the plate voltage eb the. b+ a b- ■=^ Equivalent audioloadFig. 5.—Series type generating circuit modulator tubes must supply not only the conductive current 4,but also the charging ciurent to the condenser. As a result, thegenerating unit as a whole is behaving as an impedance with acapacity component. Another type of generating circuit is shown in Fig. 6, which maybe used in radio telephone sets. It may be described as a circuit
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