Deep Dive: T7C08
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.
Why Other Answers 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.
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 Example
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.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T7C
Reference: 2022-2026 Question Pool · T7 - Practical circuits
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T7C topic.