*Question G4A07:
What happens as a receiver’s noise reduction control level is increased?*  

*Correct Answer is  A: Received signals may become distorted*  

### AI Response: (may contain errors)  

When a receiver's noise reduction control level is increased, the goal is to reduce the background noise and make the desired signals clearer. However, this process can also lead to some unintended consequences:

1. **Correct Answer: A: Received signals may become distorted**
   - Noise reduction techniques often involve digital signal processing (DSP) that can alter the audio characteristics of the received signal. As the noise reduction level is increased, the DSP may start to affect the actual signal, leading to distortion. This is because the algorithms used to reduce noise might inadvertently modify parts of the signal that are similar to noise.

2. **Why the other choices are incorrect:**
   - **B: Received frequency may become unstable**
     - Noise reduction does not affect the frequency stability of the receiver. Frequency stability is typically a function of the receiver's local oscillator and is not influenced by noise reduction settings.
   - **C: CW signals may become severely attenuated**
     - While noise reduction can affect the quality of the signal, it does not specifically target CW (Continuous Wave) signals for attenuation. Attenuation would imply a reduction in signal strength, which is not a direct result of noise reduction.
   - **D: Received frequency may shift several kHz**
     - Noise reduction does not cause frequency shifts. Frequency shifts are related to issues with the receiver's tuning or local oscillator, not the noise reduction process.

In summary, increasing the noise reduction level can lead to signal distortion because the process of reducing noise can inadvertently alter the desired signal. This is why option A is the correct answer.