*Question G4E06:
What is one disadvantage of using a shortened mobile antenna as opposed to a full-size antenna?*  

*Correct Answer is  C: Operating bandwidth may be very limited*  

### AI Response: (may contain errors)  

The correct answer to the question about the disadvantage of using a shortened mobile antenna is:

**C: Operating bandwidth may be very limited.**

### Explanation of the Correct Answer:
- **Shortened antennas** are designed to be more compact than full-size antennas, which often leads to a **narrower bandwidth**. This is because the physical size of the antenna is directly related to its resonant frequency and bandwidth. A full-size antenna can efficiently radiate over a wider range of frequencies, while a shortened antenna may only perform well at a specific frequency or a very limited range around it.

### Explanation of the Incorrect Choices:
- **A: Short antennas are more likely to cause distortion of transmitted signals.**
  - While shortened antennas can have some distortion, this is not a primary disadvantage compared to bandwidth limitations. Distortion can occur in any antenna design, but it is not a defining characteristic of shortened antennas.

- **B: Q of the antenna will be very low.**
  - This statement is incorrect. In fact, shortened antennas typically have a **high Q factor**. A high Q indicates a narrow bandwidth, which is the opposite of what this choice suggests. A high Q means the antenna is more selective in frequency, leading to limited bandwidth.

- **D: Harmonic radiation may increase.**
  - While shortened antennas can sometimes radiate harmonics, this is not a guaranteed disadvantage. Harmonic radiation can occur in any antenna design, and it is not a specific issue with shortened antennas. The primary concern with shortened antennas is their limited bandwidth.

### Summary:
- The main disadvantage of shortened mobile antennas is their **limited operating bandwidth** due to their physical size and design. This can affect performance in applications requiring a broader frequency range. 

### Useful Rule of Thumb:
- A general rule is that the **bandwidth of an antenna** is inversely proportional to its Q factor. Higher Q (narrower bandwidth) is often found in smaller antennas, while lower Q (wider bandwidth) is associated with larger antennas.