*Question G2E05:
What is the standard sideband for JT65, JT9, FT4, or FT8 digital signal when using AFSK?*  

*Correct Answer is  B: USB*  

### AI Response: (may contain errors)  

In digital modes like JT65, JT9, FT4, and FT8, the standard sideband used is Upper Sideband (USB). Here's why:

1. **Correct Answer: USB**
   - **Why USB is correct:**  
     Digital modes such as JT65, JT9, FT4, and FT8 are typically used on HF bands where USB is the standard sideband for data and digital communications. This is because USB provides a consistent convention across different bands and modes, simplifying setup and operation.

2. **Why the other choices are incorrect:**
   - **LSB (Lower Sideband):**  
     LSB is commonly used for voice communications on HF bands below 10 MHz, such as 160, 80, and 40 meters. However, for digital modes like JT65, JT9, FT4, and FT8, USB is preferred regardless of the band.
   - **DSB (Double Sideband):**  
     DSB transmits both upper and lower sidebands simultaneously, which is not efficient for digital modes. These modes require a single sideband to minimize bandwidth and interference.
   - **SSB (Single Sideband):**  
     While SSB refers to both USB and LSB, it is not specific enough. The question asks for the standard sideband, which is USB for these digital modes.

3. **Useful Rule of Thumb:**
   - For most digital modes on HF, use USB. This is a standard practice that helps ensure compatibility and reduces confusion when setting up digital communications.