*Question G8C12:
Which type of code is used for sending characters in a PSK31 signal?*  

*Correct Answer is  A: Varicode*  

### AI Response: (may contain errors)  

In PSK31, a digital mode used in amateur radio, characters are sent using a type of code called **Varicode**. Here's why:

1. **Why the correct answer is correct:**
   - **Varicode** is specifically designed for PSK31 to efficiently encode characters. It uses variable-length codes where more common characters are represented by shorter codes, and less common characters by longer codes. This helps in reducing the average transmission time and bandwidth usage.

2. **Why the other choices are incorrect:**
   - **Viterbi**: This is an algorithm used for error correction in digital communications, not for encoding characters in PSK31.
   - **Volumetric**: This term does not relate to any known coding scheme in digital communications.
   - **Binary**: While Varicode uses binary sequences, simply stating "Binary" is too broad and does not specify the unique variable-length encoding used in PSK31.

3. **Useful Information:**
   - Varicode is efficient for PSK31 because it minimizes the length of the transmission for common characters, which is crucial for low-bandwidth operations typical in amateur radio.

Understanding Varicode's role in PSK31 helps in appreciating how digital modes optimize communication efficiency.