*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 use a rule of thumb for Morse Code bandwidth:

- The bandwidth in hertz is approximately equal to the WPM multiplied by 4.

This rule of thumb accounts for the fact that Morse Code consists of a series of dots and dashes, and the bandwidth is influenced by the speed at which these are sent.

**Calculation:**

Given:
- Speed = 13 WPM

The approximate bandwidth is calculated as:
$$
\text{Bandwidth} = 13 \, \text{WPM} \times 4 = 52 \, \text{Hz}
$$

**Explanation of Choices:**

- **A: 13 Hz**  
  This choice assumes a 1:1 ratio of WPM to bandwidth, which is incorrect. The bandwidth is not equal to the WPM.

- **B: 26 Hz**  
  This choice assumes a 2:1 ratio of WPM to bandwidth, which is also incorrect. The bandwidth is not half of the WPM multiplied by 4.

- **C: 52 Hz**  
  This is the correct answer, as it uses the rule of thumb that the bandwidth is approximately 4 times the WPM.

- **D: 104 Hz**  
  This choice assumes an 8:1 ratio of WPM to bandwidth, which is incorrect. The bandwidth is not double the correct value.

By using the rule of thumb, you can quickly determine that the correct bandwidth for a 13-WPM Morse Code transmission is approximately 52 Hz.