What is the function of the Variable Frequency Oscillator (VFO) circuit in a transceiver?

The Variable Frequency Oscillator (VFO) is the heart of a transceiver's tuning mechanism. It generates a stable but adjustable radio frequency that dictates exactly where the radio transmits and receives. When you turn the main tuning dial on your radio to change stations or channels, you are directly adjusting the VFO. It acts as the master clock for the radio's operating frequency. Other options describe different circuits entirely. For example, injecting a variable frequency for CW reception is the job of a Beat Frequency Oscillator (BFO), while generating single sideband signals relies on a modulator.