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

*Correct Answer is  A: Single sideband*  

### AI Response: (may contain errors)  

Single sideband (SSB) is the correct answer because it uses the narrowest bandwidth among the given options. Here's why:

1. **Single Sideband (SSB):**
   - SSB is a form of amplitude modulation (AM) that eliminates one of the sidebands and the carrier, leaving only a single sideband. This significantly reduces the bandwidth.
   - The typical bandwidth for SSB is about 2.4 kHz for voice communications.

2. **Vestigial Sideband (VSB):**
   - VSB is a type of amplitude modulation that retains a portion of the suppressed sideband. It is commonly used in television broadcasting.
   - The bandwidth of VSB is wider than SSB because it includes a vestige of the other sideband.

3. **Phase Modulation (PM):**
   - PM is a form of angle modulation where the phase of the carrier signal is varied in accordance with the modulating signal.
   - The bandwidth of PM is generally wider than SSB and depends on the modulation index.

4. **Frequency Modulation (FM):**
   - FM is another form of angle modulation where the frequency of the carrier wave is varied by the modulating signal.
   - FM typically requires a much wider bandwidth than SSB. For example, narrowband FM (NBFM) used in amateur radio might have a bandwidth of about 12.5 kHz, while commercial FM broadcasting uses about 200 kHz.

**Rule of Thumb:**
- **SSB**: Narrowest bandwidth, typically around 2.4 kHz.
- **VSB**: Wider than SSB due to partial sideband retention.
- **PM and FM**: Generally require more bandwidth than SSB, with FM being the widest among common modulation types.

In summary, SSB is the most bandwidth-efficient mode among the options provided, making it the correct answer.