What is the function of a product detector?

A product detector is specifically designed for demodulating signals that have been modulated using phase-shift methods like single sideband (SSB) or continuous wave (CW). When dealing with SSB signals, the product detector effectively mixes the incoming RF signal with a local oscillator signal, which results in the recovery of the original audio frequency (AF) signal. This mixing process takes advantage of the way the SSB signal carries the modulation information, allowing for effective demodulation and clarity in audio output.

In the case of CW signals, which are essentially on-off keying of a carrier frequency, the product detector can also detect changes in phase representative of those keying signals, thus allowing the reception of Morse code efficiently. This functionality is crucial for operators using these modes in ham radio.

The other options pertain to different types of modulations and their specific detection processes. For instance, phase-modulated signals are typically addressed by different demodulation techniques, while frequency modulation (FM) signals are better handled by other types of detectors designed to handle the variations in frequency rather than phase or amplitude. Additionally, combining speech and RF signals generally involves other processing methods not typically performed by a product detector.