Deep Dive: G9C07
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.
Why Other Answers 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.
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 Example
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.
Source & Coverage
Question Pool: 2023-2027 Question Pool
Subelement: G9C
Reference: 2023-2027 Question Pool · G9 - Antennas and Feed Lines
Key Concepts
Verified Content
Question from the official FCC General Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the G9C topic.