Which of the following types of antenna offers the greatest gain?
The correct answer is D: Yagi. A Yagi antenna offers the greatest gain among the listed options. Yagis are directional beam antennas with multiple elements (driven element, reflector, and one or more directors) that provide significant gain in the forward direction. A well-designed Yagi can provide 10-20 dB of gain or more. For amateur radio operators, Yagis are the standard high-gain antenna for DX work and weak-signal operation. Understanding Yagi gain helps when selecting antennas for maximum performance.
Exam Tip
Greatest gain = Yagi. Think 'Y'agi = 'Y'ields highest gain. Directional beam antenna with multiple elements provides 10-20+ dB gain. 5/8 wave vertical (~3-4 dB), isotropic (0 dB reference), J-pole (~2-3 dB) all have less gain.
Memory Aid
"Greatest gain = Yagi. Think 'Y'agi = 'Y'ields highest gain. Directional beam antenna with multiple elements (director, driven, reflector) provides 10-20+ dB gain. Best for maximum performance."
Real-World Application
You compare antennas: a 5/8 wave vertical gives you about 3 dB gain, a J-pole gives about 2 dB, but a 3-element Yagi gives you 8-10 dB gain in the forward direction. This significant gain increase makes Yagis the choice for serious DX work and weak-signal operation where maximum performance is needed.
Key Concepts
Why Other Options Are Wrong
Option A (5/8 wave vertical): Incorrect. A 5/8 wave vertical has moderate gain (about 3-4 dB) but less than a Yagi. It's omnidirectional, not a high-gain directional antenna.
Option B (Isotropic): Incorrect. An isotropic antenna is a theoretical reference with 0 dB gain - it radiates equally in all directions. It's used as a reference point, not a real high-gain antenna.
Option C (J pole): Incorrect. A J-pole is a vertical antenna with moderate gain (similar to a 1/2 wave vertical, about 2-3 dB), but much less than a Yagi. It's omnidirectional.
题目解析
The correct answer is D: Yagi. A Yagi antenna offers the greatest gain among the listed options. Yagis are directional beam antennas with multiple elements (driven element, reflector, and one or more directors) that provide significant gain in the forward direction. A well-designed Yagi can provide 10-20 dB of gain or more. For amateur radio operators, Yagis are the standard high-gain antenna for DX work and weak-signal operation. Understanding Yagi gain helps when selecting antennas for maximum performance.
考试技巧
Greatest gain = Yagi. Think 'Y'agi = 'Y'ields highest gain. Directional beam antenna with multiple elements provides 10-20+ dB gain. 5/8 wave vertical (~3-4 dB), isotropic (0 dB reference), J-pole (~2-3 dB) all have less gain.
记忆口诀
Greatest gain = Yagi. Think 'Y'agi = 'Y'ields highest gain. Directional beam antenna with multiple elements (director, driven, reflector) provides 10-20+ dB gain. Best for maximum performance.
实际应用示例
You compare antennas: a 5/8 wave vertical gives you about 3 dB gain, a J-pole gives about 2 dB, but a 3-element Yagi gives you 8-10 dB gain in the forward direction. This significant gain increase makes Yagis the choice for serious DX work and weak-signal operation where maximum performance is needed.
错误选项分析
Option A (5/8 wave vertical): Incorrect. A 5/8 wave vertical has moderate gain (about 3-4 dB) but less than a Yagi. It's omnidirectional, not a high-gain directional antenna. Option B (Isotropic): Incorrect. An isotropic antenna is a theoretical reference with 0 dB gain - it radiates equally in all directions. It's used as a reference point, not a real high-gain antenna. Option C (J pole): Incorrect. A J-pole is a vertical antenna with moderate gain (similar to a 1/2 wave vertical, about 2-3 dB), but much less than a Yagi. It's omnidirectional.
知识点
Yagi antennas, Antenna gain, Directional antennas, High-gain antennas
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.