*Question E2D02:
What information replaces signal-to-noise ratio when using the FT8 or FT4 modes in a VHF contest?*  

*Correct Answer is  D: Grid square*  

### AI Response: (may contain errors)  

In FT8 and FT4 modes, particularly during VHF contests, the information that replaces the traditional signal-to-noise ratio (S/N) is the grid square.

### Explanation of the Correct Answer:
- **Grid Square**: In VHF contests using FT8 or FT4, operators exchange their grid square locator as part of the contact information. This is crucial for contest scoring and helps determine the distance between stations. The grid square provides a geographical reference that is more relevant in these modes than the S/N ratio.

### Why the Other Choices are Incorrect:
- **A: RST report**: The RST (Readability, Strength, Tone) report is typically used in voice communications to assess the quality of the signal. In digital modes like FT8 and FT4, this report is not exchanged.
  
- **B: State abbreviation**: While state abbreviations may be relevant in some contests, they are not a standard exchange in FT8 or FT4 modes. The focus is on grid squares for VHF contests.

- **C: Serial number**: Serial numbers are often used in contests for tracking contacts, but they do not replace the S/N ratio in FT8 or FT4 modes. Instead, they are exchanged alongside the grid square.

### Summary:
In FT8 and FT4 modes during VHF contests, the grid square is the key piece of information exchanged instead of the signal-to-noise ratio. Understanding this helps you prepare for the exam and grasp the operational nuances of these digital modes.