. (The) oscillation valve in the transmission and reception of radio messages . PRACTICAL APPLICATIONS OF TKE VALVE While all vacuum valves used at present for thereception of radio messages are of the three electrode type,the old two-electrode rectifier may be used in a circuit suchas Fig. Ill, in place of the crystal rectifier D. Several different groups of curves may be plottedfor the three-electrode valve from which its operating,characteristics may be readily seen. Thus the plate voltage may be plotted against theplate current, giving curves dependent upon the temperatureof the filament,
. (The) oscillation valve in the transmission and reception of radio messages . PRACTICAL APPLICATIONS OF TKE VALVE While all vacuum valves used at present for thereception of radio messages are of the three electrode type,the old two-electrode rectifier may be used in a circuit suchas Fig. Ill, in place of the crystal rectifier D. Several different groups of curves may be plottedfor the three-electrode valve from which its operating,characteristics may be readily seen. Thus the plate voltage may be plotted against theplate current, giving curves dependent upon the temperatureof the filament, or the grid voltage may be plotted againstthe grid current. The most satisfactory curve, and the onemost commonly used for explaining the operation of the tubeis the grid-voltage, plate current curve, shown in Fig. The voltage of the plate battery was kept constantwhile the grid battery was varied at positive and negativepotentials. The above curve is important, because theexplanations at present accepted, as regards the fundamentalactions of the three-electrode vacuum valve as a detectorand amplifier in radio, are based on the operating character-istics shown in the curve. ® Supposing (in Fig. VIII) the grid potentialhas been adjusted to — 3 volts (represented byAon thediagram). Now a slight increase in grid potential willcause a large increase in plate current, as shown by thecurve. On the other hand a slight decrease in gridpotential results in only a small decrease in plate current,Thus if we employ this valve as a detector in a receivingcircuit, and the grid potential is adjusted to point A,(Fig. VIII), the rise and fall of the grid potential dueto the incoming oscillations will be duplicated in theplate circuit, with the exception that the amplitudes ofthe increase exceed those of the d
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