What is the major function of an antenna tuner (antenna coupler)?
The correct answer is A: It matches the antenna system impedance to the transceiver's output impedance. The major function of an antenna tuner (antenna coupler) is to match the antenna system impedance to the transceiver's output impedance (typically 50 ohms). When your antenna doesn't present 50 ohms to the transceiver, an antenna tuner uses variable capacitors and inductors to transform the impedance, allowing the transceiver to see a 50-ohm load. For amateur radio operators, antenna tuners allow using antennas that aren't perfectly matched, extending the usable frequency range of fixed antennas. Understanding this helps explain why tuners are useful.
Exam Tip
Antenna tuner = matches impedance. Think 'T'uner = 'T'ransforms impedance to match transceiver. Matches antenna system to 50-ohm transceiver output. Not for receiver tuning, antenna selection, or enabling TX/RX - just impedance matching.
Memory Aid
"Antenna tuner = matches impedance. Think 'T'uner = 'T'ransforms impedance. Matches antenna system impedance to transceiver's 50-ohm output. Allows using mismatched antennas efficiently."
Real-World Application
Your 40-meter dipole also works on 20 meters, but the impedance is wrong (maybe 100 ohms instead of 50). An antenna tuner transforms that 100-ohm impedance to 50 ohms, allowing your transceiver to operate efficiently. The tuner doesn't change the antenna - it matches the impedance so your transceiver sees the correct load.
Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. Antenna tuners don't help receivers automatically tune - that's a receiver function. Tuners match impedance, not receiver tuning.
Option C: Incorrect. Antennas can be used on both transmit and receive without a tuner - that's a basic antenna property, not a tuner function.
Option D: Incorrect. Tuners don't automatically select antennas - that's what antenna switches do. Tuners match impedance of the selected antenna.
题目解析
The correct answer is A: It matches the antenna system impedance to the transceiver's output impedance. The major function of an antenna tuner (antenna coupler) is to match the antenna system impedance to the transceiver's output impedance (typically 50 ohms). When your antenna doesn't present 50 ohms to the transceiver, an antenna tuner uses variable capacitors and inductors to transform the impedance, allowing the transceiver to see a 50-ohm load. For amateur radio operators, antenna tuners allow using antennas that aren't perfectly matched, extending the usable frequency range of fixed antennas. Understanding this helps explain why tuners are useful.
考试技巧
Antenna tuner = matches impedance. Think 'T'uner = 'T'ransforms impedance to match transceiver. Matches antenna system to 50-ohm transceiver output. Not for receiver tuning, antenna selection, or enabling TX/RX - just impedance matching.
记忆口诀
Antenna tuner = matches impedance. Think 'T'uner = 'T'ransforms impedance. Matches antenna system impedance to transceiver's 50-ohm output. Allows using mismatched antennas efficiently.
实际应用示例
Your 40-meter dipole also works on 20 meters, but the impedance is wrong (maybe 100 ohms instead of 50). An antenna tuner transforms that 100-ohm impedance to 50 ohms, allowing your transceiver to operate efficiently. The tuner doesn't change the antenna - it matches the impedance so your transceiver sees the correct load.
错误选项分析
Option B: Incorrect. Antenna tuners don't help receivers automatically tune - that's a receiver function. Tuners match impedance, not receiver tuning. Option C: Incorrect. Antennas can be used on both transmit and receive without a tuner - that's a basic antenna property, not a tuner function. Option D: Incorrect. Tuners don't automatically select antennas - that's what antenna switches do. Tuners match impedance of the selected antenna.
知识点
Antenna tuners, Impedance matching, Antenna couplers, Matching networks
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.