*Question E8D08:
What parameter evaluates distortion of an AFSK signal caused by excessive input audio levels?*  

*Correct Answer is  D: Intermodulation Distortion (IMD)*  

### AI Response: (may contain errors)  

To evaluate distortion of an AFSK (Audio Frequency Shift Keying) signal caused by excessive input audio levels, we look at the parameter known as Intermodulation Distortion (IMD).

### Correct Answer: Intermodulation Distortion (IMD)

- **Why IMD is correct**: 
  - IMD occurs when two or more signals interact in a non-linear system, producing additional unwanted frequencies. In the context of AFSK, excessive audio levels can cause the transmitter to operate in a non-linear region, leading to distortion of the signal. This distortion can affect the clarity and integrity of the transmitted data.

### Why the other choices are incorrect:

- **A: Signal-to-noise ratio (SNR)**:
  - SNR measures the level of the desired signal compared to the level of background noise. While a low SNR can affect the quality of a signal, it does not specifically evaluate distortion caused by excessive audio levels.

- **B: Baud error rate**:
  - The baud error rate refers to the rate at which errors occur in the transmission of symbols. It is a measure of the reliability of the data transmission but does not directly assess distortion caused by audio levels.

- **C: Repeat Request Rate (RRR)**:
  - RRR is a protocol-related parameter that indicates how often a receiver requests the retransmission of data due to errors. It is not a measure of distortion but rather a response to errors in data transmission.

### Summary:
- IMD is the correct choice because it directly relates to the distortion caused by excessive audio levels in AFSK signals.
- The other options focus on different aspects of signal quality and error rates, which do not specifically address distortion.

### Useful Rule of Thumb:
- To minimize IMD, ensure that audio levels are kept within the recommended range for your equipment, avoiding excessive input that can push the transmitter into non-linear operation.