Ham Radio General Class Practice Test

How does increasing boom length and adding directors affect a Yagi antenna?

1. Gain increases

2. Beamwidth increases

3. Weight decreases

4. Wind load decreases

The correct answer is: Gain increases

Increasing the boom length and adding directors to a Yagi antenna enhances its performance primarily by increasing its gain. The gain of a Yagi antenna is a measure of its ability to focus energy in a specific direction, which is achieved through the addition of elements that extend the overall design. As the boom length increases, the overall dimensions of the antenna change, allowing for more directors to be added. Directors are parasitic elements that fundamentally contribute to the directionality and increase in gain. When more directors are employed, the antenna effectively becomes a more focused radiator, concentrating more of the emitted energy in the desired direction rather than dispersing it omnidirectionally. This results in a higher gain, which translates to better performance in terms of signal reception and transmission to a specific target. Other factors, while affected by changes in the antenna design, do not align with the benefits of increased boom length and additional directors. For example, while beamwidth refers to the width of the main lobe of radiation, increasing gain generally leads to a tighter beamwidth. Conversely, weight and wind load tend to increase with more elements and a longer boom, rather than decrease. Thus, the increase in gain is the key performance enhancement derived from these modifications in the Yagi antenna design