*Question G8C08:
Which of the following statements is true about PSK31?*  

*Correct Answer is  B: Upper case letters use longer Varicode bit sequences and thus slow down transmission*  

### AI Response: (may contain errors)  

PSK31 is a digital mode used in amateur radio that employs phase shift keying for efficient data transmission. Let's break down the question and the answer choices.

### Correct Answer: 
**B: Upper case letters use longer Varicode bit sequences and thus slow down transmission.**

- **Explanation**: In PSK31, characters are encoded using a system called Varicode. Upper case letters require longer bit sequences compared to lower case letters. This means that when transmitting upper case letters, the overall transmission speed decreases because more bits are needed to represent each character. Thus, the correct answer highlights the impact of character encoding on transmission efficiency.

### Why the Other Choices are Incorrect:

- **A: Upper case letters are sent with more power**  
  - **Explanation**: The power used in PSK31 transmission is not dependent on whether the letters are upper or lower case. The transmission power is determined by the transmitter settings and not the character case.

- **C: Error correction is used to ensure accurate message reception**  
  - **Explanation**: PSK31 does not inherently include error correction. It relies on the robustness of the modulation scheme and the signal-to-noise ratio for reliable communication. While some digital modes do use error correction, PSK31 does not.

- **D: Higher power is needed as compared to RTTY for similar error rates**  
  - **Explanation**: PSK31 is generally more efficient than RTTY (Radio Teletype) in terms of bandwidth and power usage. It can achieve similar error rates at lower power levels due to its more efficient modulation scheme. Therefore, this statement is incorrect.

### Summary:
- PSK31 uses Varicode, where upper case letters take longer to transmit due to longer bit sequences.
- The other options misrepresent the characteristics of PSK31 regarding power usage, error correction, and efficiency compared to RTTY.

This understanding of PSK31 and its encoding will help you answer related questions on the Extra Class exam effectively.