*Question E8D04:
What is the primary effect of extremely short rise or fall time on a CW signal?*  

*Correct Answer is  C: The generation of key clicks*  

### AI Response: (may contain errors)  

The correct answer to the question about the primary effect of extremely short rise or fall time on a CW (Continuous Wave) signal is **C: The generation of key clicks**.

### Explanation of the Correct Answer:
- **Key clicks** are abrupt changes in the signal when a CW operator keys their transmitter. When the rise or fall time is extremely short, the signal transitions from off to on (or vice versa) very quickly. This rapid change creates sharp edges in the waveform, which can generate unwanted frequency components (harmonics) that manifest as key clicks. These clicks can make it more difficult for other operators to copy the signal clearly.

### Why the Other Choices are Incorrect:
- **A: More difficult to copy**  
  While key clicks can make a signal harder to copy, the primary effect of short rise or fall times is the generation of key clicks themselves, not the difficulty in copying. The key clicks are the direct result of the fast transitions.

- **B: The generation of RF harmonics**  
  Although short rise and fall times can lead to the generation of harmonics, the term "key clicks" specifically refers to the audible artifacts produced during the keying process. The generation of harmonics is a broader effect and not the primary concern in this context.

- **D: More difficult to tune**  
  Short rise or fall times do not inherently make a signal more difficult to tune. Tuning is primarily affected by the frequency stability and bandwidth of the signal, not the speed of the rise or fall times.

### Summary:
- The primary effect of extremely short rise or fall times in a CW signal is the generation of key clicks, which are sharp, unwanted artifacts that can interfere with the clarity of the signal. Understanding this concept is crucial for effective CW operation and communication.