Radio Broadcast - 1923, August - 86 Pages, 8.5 ... - VacuumTubeEra

348 Radio Broadcastchanging the rheostat range from either 0-5 or0-50 ohms. This permits the use of any desiredcombination of tubes, from UV-igg, which consumesbut 60 milliamperes to the 2Oi's whichmay draw as high as one ampere. Of course,it is expected that the receiver' will be used withdry-battery tubes, and compartments havebeen provided for both filament and platebatteries.An operating switch located on the lowerright corner of the panel controls the filamentand output circuits in such a manner that whenthis switch is pulled all the way out, all fourtubes are lighted, and when the switch is pulledbut half way out only three tubes are lighted.With the switch in the latter condition, thetantset may be used with head telephones for dis-reception, or with a loud speaker for localreception. An "Aerial Switch," located at theextreme left of the panel, controls a set of smallmica condensers which are necessary to providefor the variation in wavelength range incidentto the use of the set in various locations. Underall circumstances, it is possible by means ofthis switch to tune in the complete wavelengthrange of 200 to 600 meters. For the directcontrol of wavelength, two dials with the usualGrebe tangent wheel verniers are used. Oneof these, the "Secondary Wavelength Dial,"is calibrated directly in wavelengths, thusfacilitating speed and accuracy in tuning todistant stations of known wavelength but lowaudibility. Tuning of the primary circuit is accomplishedwith a similar dial, while the .controlof regeneration is effected throughthe movement of the small tangentwheel centrally located betweenthe wavelengthA dials.feature well worthy of mentionis the manner in which twoor more of these receivers operatein close proximity of oneanother. Three of these receiverswere installed in one room,and operated simultaneouslywithout any material effect ofneradiation being noticeable.For example,it was possible totune in one set to WEAF, andthen proceed to tune the secondand third sets to the same wavelengthwithout causing a disturbance.