Ham Radio General Class Practice Test

What configuration of the loops does a two-element quad antenna need to operate as a beam antenna?

1. The driven element must be fed with a balun transformer

2. The driven element must be open-circuited on the side opposite the feed point

3. The reflector element must be approximately 5% shorter than the driven element

4. The reflector element must be approximately 5% longer than the driven element

The correct answer is: The reflector element must be approximately 5% longer than the driven element

A two-element quad antenna operates effectively as a beam antenna when configured with specific dimensions and relationships between its elements. The correct configuration requires that the reflector element is approximately 5% longer than the driven element. This size difference is critical for achieving the desired directional behavior of the antenna. The reflector serves to enhance the forward gain and reduce radiation in the opposite direction. By making the reflector longer, it provides a phase shift in the reflected waves, which reinforces the signal constructively in the direction of the driven element (which is the radiating part of the antenna). Conversely, the driven element is typically adjusted for resonance at the desired frequency, while the length of the reflector compensates to create an effective beam pattern. The specified 5% length difference is a guideline that helps optimize the antenna’s performance, ensuring that it operates efficiently and provides the anticipated directional gain. Understanding the relationship between the elements in a two-element quad is essential for both construction and operation, as these adjustments ultimately impact the antenna's radiation pattern.