What is the primary effect of increasing boom length and adding directors to a Yagi antenna?
The correct answer is A: Gain increases. The primary effect of increasing boom length and adding directors to a Yagi antenna is that gain increases. More directors and longer boom create more forward gain. For amateur radio operators, this is why longer Yagis have more gain. Understanding this helps when designing Yagi antennas.
Exam Tip
Longer boom + more directors = gain increases. Think 'L'onger 'B'oom + 'M'ore 'D'irectors = 'L'arger 'G'ain. More directors and longer boom create more forward gain. Not beamwidth increase, not F/B decrease, not lower frequency - just gain increases.
Memory Aid
"Longer boom + more directors = gain increases. Think 'L'onger 'B'oom + 'M'ore 'D'irectors = 'L'arger 'G'ain. More directors and longer boom create more forward gain. Primary effect of adding elements."
Real-World Application
A Yagi antenna: Adding more directors and increasing boom length increases the forward gain. A 3-element Yagi might have 7 dBi gain, while a 10-element Yagi might have 15 dBi gain. More elements and longer boom create more gain - this is the primary effect. Gain increases with more directors and longer boom.
Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. Beamwidth doesn't increase - it decreases (narrows) as gain increases. Beamwidth increase is wrong.
Option C: Incorrect. Front-to-back ratio doesn't decrease - it typically increases with more elements. Decrease is wrong.
Option D: Incorrect. Resonant frequency doesn't get lower - it stays roughly the same (determined by element lengths). Lower frequency is wrong.
题目解析
The correct answer is A: Gain increases. The primary effect of increasing boom length and adding directors to a Yagi antenna is that gain increases. More directors and longer boom create more forward gain. For amateur radio operators, this is why longer Yagis have more gain. Understanding this helps when designing Yagi antennas.
考试技巧
Longer boom + more directors = gain increases. Think 'L'onger 'B'oom + 'M'ore 'D'irectors = 'L'arger 'G'ain. More directors and longer boom create more forward gain. Not beamwidth increase, not F/B decrease, not lower frequency - just gain increases.
记忆口诀
Longer boom + more directors = gain increases. Think 'L'onger 'B'oom + 'M'ore 'D'irectors = 'L'arger 'G'ain. More directors and longer boom create more forward gain. Primary effect of adding elements.
实际应用示例
A Yagi antenna: Adding more directors and increasing boom length increases the forward gain. A 3-element Yagi might have 7 dBi gain, while a 10-element Yagi might have 15 dBi gain. More elements and longer boom create more gain - this is the primary effect. Gain increases with more directors and longer boom.
错误选项分析
Option B: Incorrect. Beamwidth doesn't increase - it decreases (narrows) as gain increases. Beamwidth increase is wrong. Option C: Incorrect. Front-to-back ratio doesn't decrease - it typically increases with more elements. Decrease is wrong. Option D: Incorrect. Resonant frequency doesn't get lower - it stays roughly the same (determined by element lengths). Lower frequency is wrong.
知识点
Yagi antenna, Boom length, Adding directors, Gain increase
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.