*Question G9C03:
How do the lengths of a three-element Yagi reflector and director compare to that of the driven element?*  

*Correct Answer is  A: The reflector is longer, and the director is shorter*  

### AI Response: (may contain errors)  

In a three-element Yagi antenna, the lengths of the elements are designed to optimize the antenna's performance. Here's a breakdown of the correct answer and the reasoning behind it:

### Correct Answer: A - The reflector is longer, and the director is shorter

1. **Why the correct answer is correct:**
   - The **reflector** is typically longer than the driven element. Its purpose is to reflect the radio waves, enhancing the forward gain of the antenna.
   - The **director** is shorter than the driven element. It helps to focus the radio waves in the forward direction, increasing the antenna's directivity and gain.
   - This configuration allows the Yagi antenna to achieve better performance in terms of gain and directivity.

### Why the other choices are incorrect:

- **B: The reflector is shorter, and the director is longer**
  - This is incorrect because the reflector must be longer to effectively reflect signals, while the director must be shorter to direct signals forward.

- **C: They are all the same length**
  - This is incorrect as having all elements the same length would not optimize the antenna's performance. The differences in length are crucial for the desired radiation pattern.

- **D: Relative length depends on the frequency of operation**
  - While the lengths of the elements do vary with frequency, the general rule remains that the reflector is longer and the director is shorter relative to the driven element. This choice is misleading as it suggests that the lengths could be the same or reversed, which is not the case.

### Useful Rules of Thumb:
- The length of the driven element is typically about half the wavelength ($\lambda/2$) of the frequency of operation.
- The reflector is usually about 5-10% longer than the driven element.
- The director is typically about 5-10% shorter than the driven element.

These relationships help ensure that the Yagi antenna operates efficiently and effectively at its intended frequency.