In an SSB/CW receiver, what is the purpose of the signal generated by the local oscillator?

The local oscillator (LO) provides a stable, pure sine wave frequency that changes when the operator turns the tuning dial. This LO signal is fed directly into the mixer stage of the receiver. Inside the mixer, the LO signal is combined with the incoming radio frequency (RF) signal from the antenna. The mathematical difference between these two signals produces a constant intermediate frequency (IF), which remains exactly the same regardless of what RF frequency the radio is tuned to. This fixed IF allows downstream components to efficiently amplify and filter the signal without needing to be retuned for every new station. The LO is strictly for this RF-to-IF conversion and does not produce audio or CW sidetones directly.