*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)  

A shortened mobile antenna is often used for convenience and portability, but it comes with certain trade-offs compared to a full-size antenna. Let's explore why the correct answer is "Operating bandwidth may be very limited" and why the other choices are incorrect.

### Correct Answer: C: Operating bandwidth may be very limited

1. **Explanation**:  
   - A shortened antenna has a higher Q factor, which means it is more selective and has a narrower bandwidth. The Q factor is defined as:
     $$ Q = \frac{f_0}{BW} $$
     where $f_0$ is the resonant frequency and $BW$ is the bandwidth.
   - A higher Q results in a smaller bandwidth, meaning the antenna will only perform well over a narrow range of frequencies. This can be a disadvantage if you need to operate over a wide range of frequencies.

### Why the Other Choices are Incorrect:

1. **Choice A: Short antennas are more likely to cause distortion of transmitted signals**  
   - Distortion of transmitted signals is not typically a direct consequence of using a shortened antenna. Distortion is more often related to issues like non-linear amplification or poor modulation techniques.

2. **Choice B: Q of the antenna will be very low**  
   - This is incorrect because a shortened antenna actually has a higher Q factor, not a lower one. A higher Q means a narrower bandwidth, as explained above.

3. **Choice D: Harmonic radiation may increase**  
   - Harmonic radiation is more related to the design and tuning of the antenna and transmitter, rather than the physical length of the antenna. While a poorly designed shortened antenna might have issues, increased harmonic radiation is not a direct consequence of simply shortening the antenna.

In summary, the main disadvantage of a shortened mobile antenna is its limited operating bandwidth due to a higher Q factor, making it less versatile across a range of frequencies.