*Question G8A07:
Which of the following phone emissions uses the narrowest bandwidth?*  

*Correct Answer is  A: Single sideband*  

### AI Response: (may contain errors)  

To determine which phone emission uses the narrowest bandwidth, let's analyze each option:

### Correct Answer: A - Single Sideband (SSB)

- **Why it's correct**: 
  - Single Sideband (SSB) is a refinement of amplitude modulation (AM) that eliminates one of the sidebands and the carrier. This results in a significant reduction in bandwidth. The bandwidth of SSB is typically about $3 \times f_m$, where $f_m$ is the highest frequency of the modulating signal. 
  - For example, if the audio signal has a maximum frequency of 3 kHz, the bandwidth would be approximately $3 \times 3 \text{ kHz} = 9 \text{ kHz}$.

### Why the other choices are incorrect:

- **B - Vestigial Sideband (VSB)**:
  - Vestigial Sideband modulation retains a portion of one sideband and the carrier, which results in a wider bandwidth than SSB. The bandwidth is typically slightly less than that of standard AM but still greater than SSB.

- **C - Phase Modulation (PM)**:
  - Phase modulation can have a variable bandwidth depending on the modulation index and the frequency of the modulating signal. Generally, it requires more bandwidth than SSB, especially when the modulation index is high.

- **D - Frequency Modulation (FM)**:
  - Frequency modulation has a much wider bandwidth compared to SSB. According to Carson's Rule, the bandwidth of an FM signal can be estimated as:
  $$BW_{FM} = 2 \times (f_{\Delta} + f_m)$$
  where:
  - $f_{\Delta}$ = peak frequency deviation
  - $f_m$ = maximum frequency of the modulating signal
  - This results in a bandwidth that is significantly larger than that of SSB.

### Summary:
- **SSB** is the most bandwidth-efficient phone emission, making it the correct answer.
- **VSB**, **PM**, and **FM** all require more bandwidth than SSB, making them incorrect choices. 

Understanding these differences is crucial for the Extra Class exam and practical amateur radio operations.