*Question T1B09:
[97.101(a), 97.301(a-e)] Why should you not set your transmit frequency to be exactly at the edge of an amateur band or sub-band?*  

*Correct Answer is  D: All these choices are correct*  

### AI Response: (may contain errors)  

To understand why you should not set your transmit frequency exactly at the edge of an amateur band or sub-band, let's analyze the correct answer and the other choices.

### Correct Answer: D - All these choices are correct

1. **Calibration Error**: 
   - Transmitters may have slight inaccuracies in their frequency displays. Setting your frequency exactly at the edge could lead to unintentional operation outside the band due to this error.

2. **Modulation Sidebands**: 
   - When you transmit, your signal generates sidebands. If you transmit right at the edge, these sidebands could extend beyond the band limits, causing interference to other services or users.

3. **Frequency Drift**: 
   - Transmitters can experience frequency drift due to temperature changes or other factors. By not operating at the exact edge, you provide a buffer to ensure that any drift does not push your signal outside the allowed frequency range.

### Why the Other Choices Are Incorrect

- **A: To allow for calibration error in the transmitter frequency display**: 
  - This is a valid reason, but it is only one part of the overall rationale. It does not encompass the full scope of why you should avoid the band edge.

- **B: So that modulation sidebands do not extend beyond the band edge**: 
  - This is also a valid reason, but again, it is just one aspect of the broader issue of ensuring compliance and preventing interference.

- **C: To allow for transmitter frequency drift**: 
  - This is another valid point, but it does not cover the other important factors involved.

### Summary

The correct answer is D because all the reasons provided in A, B, and C contribute to the overall principle of responsible amateur radio operation. By avoiding the exact edge of the band, you ensure compliance with regulations, minimize interference, and account for potential inaccuracies in your equipment.

### Rules of Thumb

- Always leave a small buffer (e.g., a few kHz) from the band edge when selecting your transmit frequency.
- Regularly check and calibrate your equipment to ensure accurate frequency settings.