*Question E4D09:
What is the purpose of the preselector in a communications receiver?*  

*Correct Answer is  C: To increase the rejection of signals outside the band being received*  

### AI Response: (may contain errors)  

The purpose of the preselector in a communications receiver is to increase the rejection of signals outside the band being received. Let's break down why this is the correct answer and why the other choices are incorrect:

### Correct Answer: C
- **Increase Rejection of Signals Outside the Band**:  
  A preselector is a tunable filter placed before the first RF amplifier stage in a receiver. Its main function is to allow only the desired frequency band to pass through while attenuating signals from other frequencies. This helps in reducing interference from strong out-of-band signals, which can cause issues like intermodulation distortion.

### Why Other Choices Are Incorrect:
- **Choice A: To store frequencies that are often used**  
  This is incorrect because storing frequencies is a function of a memory system or frequency synthesizer, not a preselector. A preselector does not store frequencies; it filters them.

- **Choice B: To provide broadband attenuation before the first RF stage to prevent intermodulation**  
  While a preselector does help in preventing intermodulation by filtering out unwanted signals, it is not designed to provide broadband attenuation. Instead, it selectively attenuates out-of-band signals, not all signals.

- **Choice D: To allow selection of the optimum RF amplifier device**  
  This is incorrect because selecting an RF amplifier device is a design choice made during the construction of the receiver. A preselector does not play a role in choosing the RF amplifier; it is used to filter signals.

### Summary
The preselector is crucial for improving the selectivity of a receiver by filtering out unwanted signals before they reach the RF amplifier, thus enhancing the receiver's performance in crowded frequency environments.