Question E1A02:
[97.301, 97.305] When using a transceiver that displays the carrier frequency of phone signals, which of the following displayed frequencies represents the lowest frequency at which a properly adjusted LSB emission will be totally within the band?  

Choices:  
A: The exact lower band edge  
B: 300 Hz above the lower band edge  
C: 1 kHz above the lower band edge  
D: 3 kHz above the lower band edge    

Correct Answer is  D: 3 kHz above the lower band edge  

To keep an LSB signal entirely inside the band, remember that an LSB signal occupies spectrum from the suppressed carrier frequency downward by the audio bandwidth.

Why D is correct (3 kHz above the lower band edge):
- For LSB, the RF spectrum extends from $f_c$ down to $f_c - B$, where $f_c$ is the suppressed carrier (the displayed frequency) and $B$ is the audio bandwidth (assume $B \approx 3\ \text{kHz}$ for exam purposes).
- To keep all energy inside the band whose lower edge is $f_\text{low}$, you need:
  $$f_c - B \ge f_\text{low} \;\Rightarrow\; f_c \ge f_\text{low} + 3\ \text{kHz}.$$
- Therefore, the lowest safe displayed frequency is 3 kHz above the lower band edge.

Why the other choices are incorrect:
- A: The exact lower band edge → Your LSB energy would extend about 3 kHz below the band, which is out of band.
- B: 300 Hz above the lower band edge → Still about 2.7 kHz of your signal would be out of band.
- C: 1 kHz above the lower band edge → Still about 2 kHz of your signal would be out of band.

Useful formulas and rules of thumb:
- Occupied spectrum:
  - LSB: $[f_c - B,\ f_c]$
  - USB: $[f_c,\ f_c + B]$
- With $B \approx 3\ \text{kHz}$ (exam rule):
  - Near a lower band edge:
    - LSB: set dial at least $+3$ kHz above the edge.
    - USB: you can set the dial at the edge (since energy goes up in frequency).
  - Near an upper band edge:
    - USB: set dial at least $-3$ kHz below the edge.
    - LSB: you can set the dial at the edge (since energy goes down in frequency).

This ensures compliance with 97.301/97.305 by keeping all transmitted energy inside the authorized band segment.