*Question G4D11:
How close to the upper edge of a band’s phone segment should your displayed carrier frequency be when using 3 kHz wide USB?*  

*Correct Answer is  B: At least 3 kHz below the edge of the band*  

### AI Response: (may contain errors)  

When using Upper Sideband (USB) mode, the carrier frequency is suppressed, and the transmitted signal occupies a bandwidth above the carrier frequency. For a 3 kHz wide USB signal, the entire signal is located above the carrier frequency.

### Explanation:

1. **Correct Answer: At least 3 kHz below the edge of the band (Choice B)**
   - In USB, the signal's bandwidth extends from the carrier frequency upwards. Therefore, to ensure the entire 3 kHz signal stays within the band, the carrier frequency must be at least 3 kHz below the upper edge of the band. This ensures that the highest frequency component of the signal does not exceed the band limit.

2. **Why the Other Choices are Incorrect:**
   - **Choice A: At least 3 kHz above the edge of the band**
     - This would place the entire signal outside the band, which is not allowed.
   - **Choice C: At least 1 kHz above the edge of the segment**
     - This would also place the entire signal outside the band, as the carrier frequency itself would be above the band edge.
   - **Choice D: At least 1 kHz below the edge of the segment**
     - This would not provide enough room for the entire 3 kHz signal to fit within the band, as the uppermost frequency would extend 2 kHz beyond the band edge.

### Rule of Thumb:
- For USB, ensure the carrier frequency is at least the bandwidth of the signal below the upper band edge. For a 3 kHz wide signal, this means setting the carrier frequency at least 3 kHz below the band edge.