*Question T8A05:
Which of the following types of signal has the narrowest bandwidth?*  

*Correct Answer is  C: CW*  

### AI Response: (may contain errors)  

To determine which type of signal has the narrowest bandwidth, let's analyze each option:

1. **Correct Answer: CW (Continuous Wave)**  
   - **Explanation**: CW signals are essentially on-off keying of a carrier wave, which means they have a very narrow bandwidth. The bandwidth of a CW signal is typically around $1$ Hz or less, depending on the keying speed. This is because the signal consists of a single frequency that is turned on and off, resulting in minimal frequency spread.

2. **Why the Other Choices Are Incorrect**:
   - **A: FM voice**:  
     - **Explanation**: Frequency Modulation (FM) voice signals have a much wider bandwidth due to the nature of frequency modulation. The bandwidth can be calculated using Carson's Rule:  
     $$BW = 2(\Delta f + f_m)$$  
     where $\Delta f$ is the frequency deviation and $f_m$ is the maximum modulating frequency. This results in a bandwidth that is significantly wider than CW.
   
   - **B: SSB voice (Single Sideband)**:  
     - **Explanation**: SSB voice signals also have a wider bandwidth than CW. The typical bandwidth for SSB is about $2.7$ kHz, which is necessary to accommodate the voice frequencies being transmitted. SSB is more efficient than AM but still wider than CW.
   
   - **D: Slow-scan TV (SSTV)**:  
     - **Explanation**: Slow-scan TV signals have the widest bandwidth among the options listed. SSTV typically requires a bandwidth of about $3$ kHz to $10$ kHz, depending on the resolution and frame rate of the image being transmitted. This is much wider than CW.

In summary, CW has the narrowest bandwidth due to its simple on-off nature, while FM voice, SSB voice, and SSTV all require significantly more bandwidth to transmit their respective information.