Question
What is the purpose of the preselector in a communications receiver?
Answer Options
- A) To store frequencies that are often used
- B) To provide broadband attenuation before the first RF stage to prevent intermodulation
- C) To increase the rejection of signals outside the band being received
- D) To allow selection of the optimum RF amplifier device
Correct Answer: C
Explanation
A preselector is a tuned circuit (or a set of switchable tuned circuits) located immediately at the very front end of a communications receiver, before the first active RF amplifier stage. Its purpose is to provide a preliminary level of frequency selection against strong, unwanted signals in other bands.
The essential purpose of the preselector is to increase the rejection of signals outside the band being received. By passing only the signals close to the desired receiving frequency and severely attenuating distant signals (e.g., strong AM or FM broadcast signals), the preselector prevents these strong out-of-band signals from reaching the sensitive RF amplifier and mixer, where they would cause overload and intermodulation distortion.
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