Which of the following devices can be used for impedance matching at radio frequencies?
The correct answer is D: All these choices are correct. Devices that can be used for impedance matching at radio frequencies include: a transformer, a Pi-network, and a length of transmission line. All three are common impedance matching methods. For amateur radio operators, these are essential for matching antennas to transmitters. Understanding this helps when designing matching networks.
Exam Tip
All three can match impedance: transformer, Pi-network, transmission line. When all listed devices can be used for impedance matching at RF, 'all of the above' is usually the answer. All are common matching methods.
Memory Aid
"All three can match impedance: Transformer, Pi-network, Transmission line. Think 'A'll 'M'atching 'M'ethods. All three are common methods for impedance matching at radio frequencies. Essential for antenna matching."
Real-World Application
You need to match a 200-ohm antenna to a 50-ohm transmitter. You can use: (1) A transformer (e.g., 4:1 transformer), (2) A Pi-network (adjustable L-network), or (3) A length of transmission line (quarter-wave transformer). All three can provide impedance matching at radio frequencies.
Key Concepts
Why Other Options Are Wrong
Option A: While correct, this is incomplete. Pi-networks and transmission lines are also used.
Option B: While correct, this is incomplete. Transformers and transmission lines are also used.
Option C: While correct, this is incomplete. Transformers and Pi-networks are also used.
题目解析
The correct answer is D: All these choices are correct. Devices that can be used for impedance matching at radio frequencies include: a transformer, a Pi-network, and a length of transmission line. All three are common impedance matching methods. For amateur radio operators, these are essential for matching antennas to transmitters. Understanding this helps when designing matching networks.
考试技巧
All three can match impedance: transformer, Pi-network, transmission line. When all listed devices can be used for impedance matching at RF, 'all of the above' is usually the answer. All are common matching methods.
记忆口诀
All three can match impedance: Transformer, Pi-network, Transmission line. Think 'A'll 'M'atching 'M'ethods. All three are common methods for impedance matching at radio frequencies. Essential for antenna matching.
实际应用示例
You need to match a 200-ohm antenna to a 50-ohm transmitter. You can use: (1) A transformer (e.g., 4:1 transformer), (2) A Pi-network (adjustable L-network), or (3) A length of transmission line (quarter-wave transformer). All three can provide impedance matching at radio frequencies.
错误选项分析
Option A: While correct, this is incomplete. Pi-networks and transmission lines are also used. Option B: While correct, this is incomplete. Transformers and transmission lines are also used. Option C: While correct, this is incomplete. Transformers and Pi-networks are also used.
知识点
Impedance matching, Transformer, Pi-network, Transmission line
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.