. Elements of radio telephony . -stic/e volve wasfre stean? anvil Fig. 9.—Steam haimner with automatically operated control valve. must have the element of amplification present or theapparatus will obviously not operate. This general fact istrue in the operation of any self-controlled system of this VACUUM TUBE OSCILLATORS 27 kind. For instance, if the sound produced by a telephonereceiver is of greater intensity than that which must beimpressed on the transmitter to produce the same sound,the system can be made to oscillate and produce a loud howl by placing the receiver near the transmitter
. Elements of radio telephony . -stic/e volve wasfre stean? anvil Fig. 9.—Steam haimner with automatically operated control valve. must have the element of amplification present or theapparatus will obviously not operate. This general fact istrue in the operation of any self-controlled system of this VACUUM TUBE OSCILLATORS 27 kind. For instance, if the sound produced by a telephonereceiver is of greater intensity than that which must beimpressed on the transmitter to produce the same sound,the system can be made to oscillate and produce a loud howl by placing the receiver near the transmitter. Hereagain we have taken a portion of the power from the con-trolled circuit and put enough back into the controlling cir-cuit to maintain the inputa/watt outputlOwatts Fig. 10.—Vacuum tube with its grid excited from an outside power source. Feedback Coupling.—In applying these principles to thevacuum tube, we must take some of the energy set freefrom the plate battery and bring it back to the grid cir-cuit where it can in turn control the putput of the platebattery. Consider Kg. 10 in which a vacuum tube is shown with itsgrid circuit connected to an outside source of power. As-siune that it takes ^ watt input to completely control theoutput of the plate battery, and that imder these conditionsthe plate battery can deliver 10 watts of power. If the grid 28 ELEMENTS OF RADIO TELEPHONY circuit is connected to a 60-cycle source of power, the poweroutput of the plate circuit will be a reproduction of theimpressed 60-cycle wave. But it is possible to take xo wattof power from the plate circuit and still, have a possible of power left. Under these conditions the systemcould be made to oscilMe without any connection to
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectradio, bookyear1922
