Ham Radio General Class Practice Test

What type of circuit is used in many FM receivers to convert signals coming from the IF amplifier to audio?

1. Product detector

2. Phase inverter

3. Mixer

4. Discriminator

The correct answer is: Discriminator

The discriminator is a crucial component in many FM receivers, as it is specifically designed to convert frequency variations of the received FM signal into corresponding amplitude variations, which are then processed as audio signals. In an FM transmission, the information is encoded by varying the frequency of the carrier wave. The discriminator effectively demodulates this signal by taking the frequency variations and translating them into voltage or current changes that can be amplified and sent to the audio output stage. Discriminators work by detecting changes in frequency and converting these changes into a more consistent audio output, which is vital for the reproduction of the original transmitted audio quality. This is particularly important in FM systems because they are more immune to signal degradation compared to AM systems, making them preferable for high-fidelity audio transmissions. Other types of circuits mentioned, such as the product detector or mixer, serve different functions in signal processing. While a product detector might be involved in other forms of modulation, it is not typically used for demodulating FM signals effectively. A phase inverter would not apply in this context as it deals with phase manipulation and is not specifically for converting FM signals into audio. Therefore, the discriminator is the correct choice for this process in FM receivers.