OCR Text |
Show THIRD TUBE IS AUDIO-FREQUENCY AMPLIFIER HY PA1 I I . GODLET lXU erica - FoVemoel Hadlo Authority Ttils i- the -' vi nth of n series of ur-tlcles ur-tlcles on the Armstrong sniver-genmt- iio reesjlioex'. A combination of three tubes mav be used In the super-regenerative receiver re-ceiver circuit. The third tube acts as an audio frequency fre-quency amplifier and is coupled to the I plate , in nit th" controller or oscll-! oscll-! lator tube through an audio frequency I transformer. Where this arrangement Is used, the filter circuit becomes essential, for the received sicrna'.s are very powerful Any of tM high pitched oscillations ;?cnnrated by tho circuits of the tube 0 will be amplified lo the point where j they may completely mar the voice or music. It i- not easy to construct the filter ' circuit. The resistances, R and H2. should he non-cr nductlve and have a value of 1 0.000 to 13.'ji. ohms each They may rbe purchased from a supply store In the form of carbon resistance rods, or they may be one of the several special spe-cial types of resistance units such as the Invite units used by the Wester., Eieciric company I Condenser f'r, should be variable of ja maximum capacity of .003 MF. This' i? s fairly large variable unlt-and rath-1 'er expensive. The Inductn ncs, Lo, Is nn iron core, having 0" value of approximately one henr; . and may be ordered from any established ma nufaclurer. Figure 6 shows a compromise clr-suit clr-suit using throe tubes. The result. with thlg last circuit will compare very favorably with those of tho circuit in the other figure. It is amply suited! for use in conjunction with the loud Speaker. The advantage gained here Is thai little, if any, of the audible o -' illation of the circuits of the tube 0 will be appnrer.t FOt R TUBES, Wi'h either nf thes? circuits a fourth tube msy be added. If this is don. a of somewhat larger capacity thun L5 pgrrJff 1 vie 5 iLl -B:i L rQ I t3E I 1 FigO 5rS j P 1 Z JL v r- CgJ THKKF-TL HK SlTRR-RKfiFA'KK ATI VK ( 1P I M S the ordinary amplifying tube will he required for the best results. For example, ex-ample, a five-watt transmitter tube such as Kadlotron UVfQl Will serve. This tube will require upward of ISO ( olts on the plate Attention is called to the grid battery bat-tery in the grid circuits of tubes R and lO. This Is a refinement which tends I to give stability to the circuits and to I induce distortion of voice and music This battery will range from LB to 6 volts, and may be changed 1 f volts at a time, thus enabling the , use of three or four dry cell:-, in series. |