Which of the following can be determined with a directional wattmeter?
The correct answer is A: Standing wave ratio. What can be determined with a directional wattmeter is standing wave ratio (SWR). Directional wattmeters measure forward and reflected power, allowing SWR calculation. For amateur radio operators, this is a primary use of directional wattmeters. Understanding this helps when measuring SWR.
Exam Tip
Directional wattmeter determines = standing wave ratio (SWR). Think 'D'irectional 'W'attmeter = 'D'etermines 'W'ave ratio (SWR). Measures forward and reflected power, allowing SWR calculation. Not front-to-back ratio, not interference, not propagation - just SWR.
Memory Aid
"Directional wattmeter determines = standing wave ratio (SWR). Think 'D'irectional 'W'attmeter = 'D'etermines 'W'ave ratio. Measures forward and reflected power, allowing SWR calculation. Primary use of directional wattmeters."
Real-World Application
You use a directional wattmeter to measure SWR. The wattmeter measures forward power (e.g., 100 watts) and reflected power (e.g., 10 watts). From these measurements, you can calculate SWR. Directional wattmeters are the standard tool for measuring SWR.
Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. Directional wattmeters don't determine antenna front-to-back ratio - that requires measuring signal strength from different directions. Front-to-back ratio needs field strength measurements.
Option C: Incorrect. Directional wattmeters don't determine RF interference - that requires spectrum analyzers or other equipment. Interference measurement is different.
Option D: Incorrect. Directional wattmeters don't determine radio wave propagation - that requires propagation monitoring. Propagation is about conditions, not power measurements.
题目解析
The correct answer is A: Standing wave ratio. What can be determined with a directional wattmeter is standing wave ratio (SWR). Directional wattmeters measure forward and reflected power, allowing SWR calculation. For amateur radio operators, this is a primary use of directional wattmeters. Understanding this helps when measuring SWR.
考试技巧
Directional wattmeter determines = standing wave ratio (SWR). Think 'D'irectional 'W'attmeter = 'D'etermines 'W'ave ratio (SWR). Measures forward and reflected power, allowing SWR calculation. Not front-to-back ratio, not interference, not propagation - just SWR.
记忆口诀
Directional wattmeter determines = standing wave ratio (SWR). Think 'D'irectional 'W'attmeter = 'D'etermines 'W'ave ratio. Measures forward and reflected power, allowing SWR calculation. Primary use of directional wattmeters.
实际应用示例
You use a directional wattmeter to measure SWR. The wattmeter measures forward power (e.g., 100 watts) and reflected power (e.g., 10 watts). From these measurements, you can calculate SWR. Directional wattmeters are the standard tool for measuring SWR.
错误选项分析
Option B: Incorrect. Directional wattmeters don't determine antenna front-to-back ratio - that requires measuring signal strength from different directions. Front-to-back ratio needs field strength measurements. Option C: Incorrect. Directional wattmeters don't determine RF interference - that requires spectrum analyzers or other equipment. Interference measurement is different. Option D: Incorrect. Directional wattmeters don't determine radio wave propagation - that requires propagation monitoring. Propagation is about conditions, not power measurements.
知识点
Directional wattmeter, Standing wave ratio, SWR, Forward/reflected power
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.