*Question E8C05:
What is the approximate bandwidth of a 13-WPM International Morse Code transmission?*  

*Correct Answer is  C: 52 Hz*  

### AI Response: (may contain errors)  

To determine the approximate bandwidth of a 13-WPM (words per minute) International Morse Code transmission, we can use the following rule of thumb:

The bandwidth (BW) in hertz for Morse Code can be estimated using the formula:

$$
BW \approx 2 \times \text{WPM}
$$

Where:
- WPM = words per minute

For a 13-WPM transmission, we can calculate the bandwidth as follows:

$$
BW \approx 2 \times 13 = 26 \text{ Hz}
$$

However, this formula gives us the minimum bandwidth. In practice, the actual bandwidth required is often wider due to factors like keying speed and signal characteristics. A more practical estimate for Morse Code transmissions is:

$$
BW \approx 4 \times \text{WPM}
$$

Using this more practical estimate:

$$
BW \approx 4 \times 13 = 52 \text{ Hz}
$$

### Explanation of the Correct Answer:
- **Correct Answer: 52 Hz**  
  This is the most accurate estimate for the bandwidth of a 13-WPM Morse Code transmission, considering the practical factors involved in signal transmission.

### Explanation of Incorrect Choices:
- **A: 13 Hz**  
  This value is too low and does not account for the necessary bandwidth for effective transmission at 13 WPM.

- **B: 26 Hz**  
  While this is the minimum bandwidth calculated using the first formula, it does not reflect the practical requirements for Morse Code transmission, which typically needs more bandwidth.

- **D: 104 Hz**  
  This value is too high for a 13-WPM transmission and would be more appropriate for much faster Morse Code speeds.

### Summary:
- The correct bandwidth for a 13-WPM Morse Code transmission is approximately 52 Hz, based on practical considerations of signal transmission. The other choices either underestimate or overestimate the required bandwidth.