What is antenna gain?
The correct answer is C: The increase in signal strength in a specified direction compared to a reference antenna. Antenna gain is the increase in signal strength in a specified direction compared to a reference antenna (typically an isotropic antenna or dipole). Gain is expressed in decibels (dB) and represents how much stronger the signal is compared to the reference. For amateur radio operators, understanding antenna gain helps when selecting antennas and predicting performance. Gain doesn't add power - it concentrates existing power in desired directions. A 6 dB gain antenna makes your signal 4 times stronger in that direction compared to a reference antenna.
Exam Tip
Antenna gain = signal strength increase in a direction. Think 'G'ain = 'G'reater signal 'G'oing in one direction. Compared to reference antenna (isotropic or dipole). Doesn't add power, doesn't require more power, not about impedance.
Memory Aid
"Antenna gain = signal strength increase in direction. Think 'G'ain = 'G'reater signal in one direction compared to reference. Expressed in dB. Doesn't add power - concentrates it."
Real-World Application
You replace an omnidirectional antenna with a 3-element Yagi that has 8 dB gain. In the forward direction, your signal is 8 dB stronger (about 6 times more powerful) than it was with the omnidirectional antenna. This doesn't mean your transmitter puts out more power - the Yagi just concentrates the same power in the forward direction, making it stronger there while reducing it in other directions.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Antennas don't add power to the transmitter - they can't create energy. Gain concentrates power in directions, it doesn't add power.
Option B: Incorrect. Antennas don't require additional power at higher frequencies - power requirements depend on the transmitter, not the antenna. Gain is about directionality, not power requirements.
Option D: Incorrect. Gain isn't about impedance increase - it's about signal strength increase. Impedance and gain are different antenna characteristics.
题目解析
The correct answer is C: The increase in signal strength in a specified direction compared to a reference antenna. Antenna gain is the increase in signal strength in a specified direction compared to a reference antenna (typically an isotropic antenna or dipole). Gain is expressed in decibels (dB) and represents how much stronger the signal is compared to the reference. For amateur radio operators, understanding antenna gain helps when selecting antennas and predicting performance. Gain doesn't add power - it concentrates existing power in desired directions. A 6 dB gain antenna makes your signal 4 times stronger in that direction compared to a reference antenna.
考试技巧
Antenna gain = signal strength increase in a direction. Think 'G'ain = 'G'reater signal 'G'oing in one direction. Compared to reference antenna (isotropic or dipole). Doesn't add power, doesn't require more power, not about impedance.
记忆口诀
Antenna gain = signal strength increase in direction. Think 'G'ain = 'G'reater signal in one direction compared to reference. Expressed in dB. Doesn't add power - concentrates it.
实际应用示例
You replace an omnidirectional antenna with a 3-element Yagi that has 8 dB gain. In the forward direction, your signal is 8 dB stronger (about 6 times more powerful) than it was with the omnidirectional antenna. This doesn't mean your transmitter puts out more power - the Yagi just concentrates the same power in the forward direction, making it stronger there while reducing it in other directions.
错误选项分析
Option A: Incorrect. Antennas don't add power to the transmitter - they can't create energy. Gain concentrates power in directions, it doesn't add power. Option B: Incorrect. Antennas don't require additional power at higher frequencies - power requirements depend on the transmitter, not the antenna. Gain is about directionality, not power requirements. Option D: Incorrect. Gain isn't about impedance increase - it's about signal strength increase. Impedance and gain are different antenna characteristics.
知识点
Antenna gain, Signal strength, Directional gain, Antenna performance
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.