On the Variation of Generated Frequency of a Triode Oscillator due to Changes in Filament Current, Grid Voltage, Plate Voltage, or External Resistance

The general expressions for the generated frequency of the grid-tuned and the plate-tuned oscillators are developed. In developing these expressions it is assumed that the grid takes a convection current and that there are external resistances in the circuits. The equations which represent the frequency of oscillation of the two types of oscillators are similar and indicate that in order to transform from one type of generator to the other it is only necessary to interchange the plate-circuit constants with the grid-circuit constants. The effect of making any change in the circuit conditions which causes the grid current to increase is observed to cause the frequency of oscillation to decrease; and likewise any change which does not affect the grid current does not affect the frequency. For fixed grid-battery voltage and plate-battery voltage the effect of decreasing the filament current below its rated value is to increase the generated frequency for both types of oscillators. This change in frequency is greatest for positive values of grid-battery voltage and low plate-battery voltage. With fixed filament current and plate-battery voltage, the effect of changing the grid-battery voltage from negative to positive values is to cause at first a decrease and then an increase in the generated frequency. This change in frequency is greatest for low plate-battery voltages and high (near rated) filament currents. For fixed filament current and grid-battery voltage the effect of increasing the plate-battery voltage is first to lower the generated frequency and then to raise it.