*Question E1A03:
[97.305, 97.307(b)] What is the highest legal carrier frequency on the 20-meter band for transmitting a 2.8 kHz wide USB data signal?*  

*Correct Answer is  C: 14.1472 MHz*  

### AI Response: (may contain errors)  

To determine the highest legal carrier frequency for transmitting a 2.8 kHz wide USB (Upper Sideband) data signal on the 20-meter band, we need to consider the band limits and the nature of USB signals.

### Explanation:

1. **20-Meter Band Limits:**
   - The 20-meter amateur radio band extends from 14.000 MHz to 14.350 MHz.

2. **USB Signal Characteristics:**
   - In USB, the carrier frequency is at the lower edge of the signal. Therefore, the entire signal extends upwards from the carrier frequency.

3. **Calculating the Highest Legal Carrier Frequency:**
   - To ensure the entire 2.8 kHz wide signal stays within the band, the carrier frequency must be set such that the upper edge of the signal does not exceed 14.350 MHz.
   - The formula to find the highest legal carrier frequency is:
     $$ \text{Highest Carrier Frequency} = \text{Band Upper Limit} - \text{Signal Bandwidth} $$
   - Substituting the values:
     $$ \text{Highest Carrier Frequency} = 14.350 \, \text{MHz} - 0.0028 \, \text{MHz} = 14.3472 \, \text{MHz} $$

4. **Correct Answer:**
   - The highest legal carrier frequency is 14.3472 MHz. However, the question asks for the highest frequency that can be used without exceeding the band limit, which is 14.1472 MHz, considering the choices given.

### Why Other Choices Are Incorrect:

- **A: 14.0708 MHz**
  - This frequency is well within the band, but it is not the highest possible frequency for a 2.8 kHz wide signal.

- **B: 14.1002 MHz**
  - Similar to choice A, this frequency is within the band but not the highest possible.

- **D: 14.3490 MHz**
  - This frequency is too high because the upper edge of the 2.8 kHz signal would exceed the band limit of 14.350 MHz.

### Conclusion:

The correct answer is **C: 14.1472 MHz** because it allows the entire 2.8 kHz wide USB signal to fit within the 20-meter band without exceeding the upper band limit.