Which instrument can be used to determine SWR?
The correct answer is D: Directional wattmeter. A directional wattmeter (also called an SWR/power meter) can be used to determine SWR. Directional wattmeters measure both forward power (power going to the antenna) and reflected power (power reflected back from the antenna), and calculate SWR from these measurements. They're the standard instrument for measuring SWR in amateur radio stations. For amateur radio operators, directional wattmeters are essential tools for antenna tuning, checking feed line performance, and ensuring proper system operation. They're more accurate and informative than simple SWR meters.
Exam Tip
Directional wattmeter = measures SWR. Think 'D'irectional 'W'attmeter = 'D'etermines 'W'ave ratio (SWR). It measures forward and reflected power to calculate SWR. Voltmeters measure voltage, ohmmeters measure resistance, and iambic pentameter is poetry, not electronics.
Memory Aid
"Directional wattmeter = Determines SWR. Think 'D'irectional 'W'attmeter = 'D'etermines 'W'ave ratio. Measures forward and reflected power to calculate SWR."
Real-World Application
You connect a directional wattmeter between your transmitter and antenna. It shows 100 watts forward power and 10 watts reflected power, which it calculates as 1.5:1 SWR. This tells you your antenna is reasonably well matched. The directional wattmeter is the standard tool for this measurement - it's what most amateurs use for SWR and power measurements.
Key Concepts
Why Other Options Are Wrong
Option A (Voltmeter): Incorrect. A voltmeter measures voltage, not SWR. While you could theoretically calculate SWR from voltage measurements on a transmission line, it's not practical and voltmeters aren't designed for this.
Option B (Ohmmeter): Incorrect. An ohmmeter measures DC resistance, not SWR. SWR is an RF measurement that requires measuring forward and reflected power.
Option C (Iambic pentameter): Incorrect. This is a humorous distractor - iambic pentameter is a poetic meter (rhythm pattern), not an electronic instrument. It's not a real measurement tool.
题目解析
The correct answer is D: Directional wattmeter. A directional wattmeter (also called an SWR/power meter) can be used to determine SWR. Directional wattmeters measure both forward power (power going to the antenna) and reflected power (power reflected back from the antenna), and calculate SWR from these measurements. They're the standard instrument for measuring SWR in amateur radio stations. For amateur radio operators, directional wattmeters are essential tools for antenna tuning, checking feed line performance, and ensuring proper system operation. They're more accurate and informative than simple SWR meters.
考试技巧
Directional wattmeter = measures SWR. Think 'D'irectional 'W'attmeter = 'D'etermines 'W'ave ratio (SWR). It measures forward and reflected power to calculate SWR. Voltmeters measure voltage, ohmmeters measure resistance, and iambic pentameter is poetry, not electronics.
记忆口诀
Directional wattmeter = Determines SWR. Think 'D'irectional 'W'attmeter = 'D'etermines 'W'ave ratio. Measures forward and reflected power to calculate SWR.
实际应用示例
You connect a directional wattmeter between your transmitter and antenna. It shows 100 watts forward power and 10 watts reflected power, which it calculates as 1.5:1 SWR. This tells you your antenna is reasonably well matched. The directional wattmeter is the standard tool for this measurement - it's what most amateurs use for SWR and power measurements.
错误选项分析
Option A (Voltmeter): Incorrect. A voltmeter measures voltage, not SWR. While you could theoretically calculate SWR from voltage measurements on a transmission line, it's not practical and voltmeters aren't designed for this. Option B (Ohmmeter): Incorrect. An ohmmeter measures DC resistance, not SWR. SWR is an RF measurement that requires measuring forward and reflected power. Option C (Iambic pentameter): Incorrect. This is a humorous distractor - iambic pentameter is a poetic meter (rhythm pattern), not an electronic instrument. It's not a real measurement tool.
知识点
Directional wattmeters, SWR measurement, Power measurement, Test equipment
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.