Ham Radio General Class Practice Test

What circuit is used to combine signals from the IF amplifier and BFO and send the result to the AF amplifier in a single-sideband receiver?

1. RF oscillator

2. IF filter

3. Balanced modulator

4. Product detector

The correct answer is: Product detector

In a single-sideband (SSB) receiver, the correct circuit to combine signals from the intermediate frequency (IF) amplifier and the beat frequency oscillator (BFO) is the product detector. The role of the product detector is to perform a process known as synchronous detection or demodulation. This operation consists of mixing the incoming IF signal with the output from the BFO. By multiplying these two signals together, the product detector effectively extracts the audio information (i.e., the original modulation) from the SSB signal while eliminating the unwanted components of the carrier frequency. The output of the product detector is a baseband signal that retains the original audio information, which is then sent to the audio frequency (AF) amplifier for further processing and amplification. This approach is crucial for accurate signal demodulation in SSB receivers because it allows for effective recovery of voice signals without the need for a carrier signal, which is rejected in SSB transmission. Other options do not fulfill this specific function; for instance, an RF oscillator generates signals at radio frequencies but does not mix them for demodulation, while IF filters are used to select specific frequency ranges after mixing. A balanced modulator typically is employed to generate SSB signals but is not