What component does a mechanical modulator vary in an RF oscillator?

In the context of a mechanical modulator in an RF (radio frequency) oscillator, capacitance is the correct component that is varied. Mechanical modulators often utilize a variable capacitor as part of the oscillator circuit. By adjusting the capacitance, the resonant frequency of the oscillator can be changed, which is essential for tuning the oscillator to the desired frequency.

As capacitance is manipulated, it affects the reactance in the LC (inductance-capacitance) circuit, directly influencing the oscillation frequency. This adjustment is critical for applications like communication systems, where different frequencies need to be generated for transmitting various signals.

The other components such as voltage, inductance, and resistance, while important in RF circuits, are not typically the primary variables adjusted by mechanical modulation in the way capacitance is. Inductance can also influence frequency, but in the context of a mechanical modulator, capacitance is the key component that is modulated to achieve tuning or frequency shifts.