*Question E4E09:
What undesirable effect can occur when using a noise blanker?*  

*Correct Answer is  C: Strong signals may be distorted and appear to cause spurious emissions*  

### AI Response: (may contain errors)  

When using a noise blanker in a radio receiver, the correct answer to the question about undesirable effects is:

**C: Strong signals may be distorted and appear to cause spurious emissions.**

### Explanation of the Correct Answer:
- **Noise Blankers** are designed to reduce impulsive noise, such as that from electrical interference or ignition noise from vehicles. However, when strong signals are present, the noise blanker can inadvertently distort these signals. This distortion can lead to the appearance of spurious emissions, which are unwanted signals that can interfere with the reception of the desired signal.

### Explanation of the Incorrect Choices:
- **A: Received audio in the speech range might have an echo effect**
  - This is not typically a result of using a noise blanker. Echo effects are more related to audio processing or delay lines rather than the operation of a noise blanker.

- **B: The audio frequency bandwidth of the received signal might be compressed**
  - Noise blankers do not compress the bandwidth of the audio signal. They primarily focus on eliminating noise spikes without altering the frequency characteristics of the desired signal.

- **D: FM signals can no longer be demodulated**
  - A noise blanker does not prevent the demodulation of FM signals. It is designed to improve the clarity of received signals by reducing noise, not to interfere with the demodulation process itself.

### Summary:
- Noise blankers can distort strong signals, leading to spurious emissions.
- They do not create echo effects, compress bandwidth, or prevent FM demodulation. 

Understanding these effects is crucial for effective operation and troubleshooting in amateur radio.