Ham Amateur Radio Technician Practice Exam

What is the primary effect of increasing boom length and adding directors to a Yagi antenna?

1. Gain increases

2. Bandwidth decreases

3. Front-to-back ratio decreases

4. Beamwidth increases

The correct answer is: Gain increases

Increasing the boom length and adding directors to a Yagi antenna primarily enhances its gain. In a Yagi design, gain is a measure of how well the antenna converts input power into radio waves in a desired direction compared to a dipole antenna. When you lengthen the boom and add directors, you effectively increase the number of elements in the antenna. Directors work to focus the signal in a specific direction, thereby improving the directivity of the antenna and boosting its gain. This structure allows the antenna to radiate more effectively in the desired direction while reducing the energy radiated in other directions. As a result, this modification results in a higher gain, leading to an improved signal strength for both transmission and reception in the targeted direction. The other potential effects of this modification, such as bandwidth and beamwidth, generally trend differently with increased boom length and added directors. Typically, bandwidth can decrease with a more focused beam, and beamwidth may narrow rather than increase due to increased directivity. Therefore, while gain is primarily enhanced through these design changes, other characteristics adjust in ways that do not support the other options given.