*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 elements are typically arranged as follows:

1. **Driven Element**: This is the element that is directly connected to the feedline and is usually resonant at the desired frequency. Its length is approximately half a wavelength ($\lambda/2$).

2. **Reflector**: The reflector is positioned behind the driven element (relative to the direction of maximum radiation). It is slightly longer than the driven element. This additional length helps to reflect radio waves back towards the driven element, enhancing forward gain.

3. **Director**: The director is placed in front of the driven element. It is slightly shorter than the driven element. This shorter length helps to direct the radio waves in the desired direction, further increasing the antenna's forward gain.

### Why the Correct Answer is Correct:
- **Correct Answer (A)**: "The reflector is longer, and the director is shorter" is correct because:
  - The reflector's longer length helps reflect energy back towards the driven element.
  - The director's shorter length helps focus the energy in the forward direction.

### Why the Other Choices are Incorrect:
- **Choice B**: "The reflector is shorter, and the director is longer" is incorrect because it would not effectively enhance the forward gain of the antenna.
- **Choice C**: "They are all the same length" is incorrect because having all elements the same length would not provide the directional characteristics typical of a Yagi antenna.
- **Choice D**: "Relative length depends on the frequency of operation" is incorrect in the context of element length relationships. While the absolute lengths depend on frequency, the relative lengths (reflector longer, director shorter) remain consistent for a given design.

### Useful Rule of Thumb:
- **Reflector Length**: Approximately 5% longer than the driven element.
- **Director Length**: Approximately 5% shorter than the driven element.

These length differences are crucial for the Yagi antenna's directional properties and gain.