What is the function of the beat frequency oscillator in a single sideband and CW receiver?

In a single sideband (SSB) and continuous wave (CW) receiver, the beat frequency oscillator (BFO) plays a crucial role in the demodulation process by generating a carrier frequency. When receiving SSB signals, which do not have a carrier, the BFO produces a frequency that is mixed with the received signal. This mixing process results in the creation of an audible signal by recreating the necessary carrier frequency needed to restore the original modulation.

In the case of CW transmission, the BFO serves a similar purpose by allowing the operator to detect the Morse code signals. By generating a specific frequency, the BFO enables the operator to hear the on-off keying of the CW signal as a tone, effectively allowing for the demodulation of the signal.

The other options are not the primary functions of the BFO. Amplification is typically handled by other stages of the receiver's circuitry; filtering noise is managed by bandpass filters or similar devices; while the BFO is integral to demodulation, its primary function is to recreate the carrier frequency needed for this process in SSB and CW communications.