. QST . was checked on phone. The front panel of this compact (12^^8 widebj 103^ deep by 6^ inches high) unit has acouple of departures from usual practice. Thefirst that hits your eje is the apparent lackof a VFO tuning knob! You stop worrying aboutthis when you discover that the VFO tuning andthe bandswitch are concentric controls (a laTV), a dodge that makes for an uncrowdedpanel. The audio gain control, instead of a largeknob matching the others in size, is a smallknurled shaft that can hardly be seen. And whynot? — the audio volume control on a trans-mitter doesnt get the steady handling
. QST . was checked on phone. The front panel of this compact (12^^8 widebj 103^ deep by 6^ inches high) unit has acouple of departures from usual practice. Thefirst that hits your eje is the apparent lackof a VFO tuning knob! You stop worrying aboutthis when you discover that the VFO tuning andthe bandswitch are concentric controls (a laTV), a dodge that makes for an uncrowdedpanel. The audio gain control, instead of a largeknob matching the others in size, is a smallknurled shaft that can hardly be seen. And whynot? — the audio volume control on a trans-mitter doesnt get the steady handling that areceiver volume control does. The rest of thecontrols are what you would expect on a trans-mitter of this type: a meter switch for the and plate current and the modulator cathodecurrent, a TUNE-CW-HET-PHONE switch(TUNE reduces power to the output stage anddisables the modulator, and HET turns on theVFO for frequency spotting or amplifier-onlykeying), a DRIVE switch for varying excitation. Fig. 2 — Simplified oscillator circuit of the hen using VFO, the crystal socket requires a shortingplug. When crystal control is used, the VFO tuned cir-cuit can be used to pull the crystal frequency slightlyand thus zero in on a net frequency. by changing the screen voltage to the driverstage, and PLATE and ANT tuning. The ANT tuning control is more than meetsthe eye. Since a pi-network output circuit isused, there is the normal need for a wide varia-tion in output capacitance. In the T-90, thecontrol turns the rotor of a 150-MAf- variablecapacitor. On the far end of the rotor shaft thereis a pin that engages a spoke on a switch shaft An additional shield cover has been removed to showthe VFO compartment (lower center). The hub andspokes at the center left drive the output-capacitorswitch shown in another photograph. The spokes aredriven by an arm on the shaft of the output tuningcapacitor at the lower left.
Size: 1547px × 1615px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectradio, bookyear1915
