What does “front-to-back ratio” mean in reference to a Yagi antenna?
The correct answer is C: The power radiated in the major lobe compared to that in the opposite direction. What 'front-to-back ratio' means in reference to a Yagi antenna is the power radiated in the major lobe compared to that in the opposite direction. Front-to-back ratio measures how much stronger forward radiation is than backward radiation. For amateur radio operators, this is an important Yagi specification. Understanding this helps when evaluating Yagi performance.
Exam Tip
Front-to-back ratio = power in major lobe vs opposite direction. Think 'F'ront-to-'B'ack = 'F'orward 'B'ackward power ratio. Measures how much stronger forward radiation is than backward radiation. Not element count, not element position, not forward/dipole gain - just forward vs backward power.
Memory Aid
"Front-to-back ratio = power in major lobe vs opposite direction. Think 'F'ront-to-'B'ack = 'F'orward 'B'ackward. Measures how much stronger forward radiation is than backward radiation. Important Yagi specification."
Real-World Application
A Yagi antenna: Forward radiation (major lobe) is 100 watts, backward radiation is 10 watts. Front-to-back ratio = 100/10 = 10:1 (or 10 dB). This measures how much stronger forward radiation is than backward radiation. Higher front-to-back ratio means less interference to stations behind the antenna. This is what front-to-back ratio means.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Front-to-back ratio isn't number of directors vs reflectors - it's a power ratio, not element count. Element count isn't the ratio.
Option B: Incorrect. Front-to-back ratio isn't relative position of driven element - it's a power ratio, not element position. Position isn't the ratio.
Option D: Incorrect. Front-to-back ratio isn't forward gain vs dipole gain - that's gain in dBd. Forward/dipole gain isn't F/B ratio.
题目解析
The correct answer is C: The power radiated in the major lobe compared to that in the opposite direction. What 'front-to-back ratio' means in reference to a Yagi antenna is the power radiated in the major lobe compared to that in the opposite direction. Front-to-back ratio measures how much stronger forward radiation is than backward radiation. For amateur radio operators, this is an important Yagi specification. Understanding this helps when evaluating Yagi performance.
考试技巧
Front-to-back ratio = power in major lobe vs opposite direction. Think 'F'ront-to-'B'ack = 'F'orward 'B'ackward power ratio. Measures how much stronger forward radiation is than backward radiation. Not element count, not element position, not forward/dipole gain - just forward vs backward power.
记忆口诀
Front-to-back ratio = power in major lobe vs opposite direction. Think 'F'ront-to-'B'ack = 'F'orward 'B'ackward. Measures how much stronger forward radiation is than backward radiation. Important Yagi specification.
实际应用示例
A Yagi antenna: Forward radiation (major lobe) is 100 watts, backward radiation is 10 watts. Front-to-back ratio = 100/10 = 10:1 (or 10 dB). This measures how much stronger forward radiation is than backward radiation. Higher front-to-back ratio means less interference to stations behind the antenna. This is what front-to-back ratio means.
错误选项分析
Option A: Incorrect. Front-to-back ratio isn't number of directors vs reflectors - it's a power ratio, not element count. Element count isn't the ratio. Option B: Incorrect. Front-to-back ratio isn't relative position of driven element - it's a power ratio, not element position. Position isn't the ratio. Option D: Incorrect. Front-to-back ratio isn't forward gain vs dipole gain - that's gain in dBd. Forward/dipole gain isn't F/B ratio.
知识点
Front-to-back ratio, Yagi antenna, Major lobe, Opposite direction
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.