Which of the following is often determined using a Smith chart?
The correct answer is C: Impedance and SWR values in transmission lines. Smith charts are often used to determine impedance and SWR values in transmission lines. The chart provides a graphical way to solve transmission line impedance problems.
Smith charts are the standard tool for transmission line impedance analysis. You can plot an impedance, then move around the chart (representing distance along the transmission line) to see how impedance changes. The chart also shows SWR circles - all points on a constant SWR circle have the same SWR value. This makes it easy to find impedance transformations, calculate SWR, design matching networks, and solve transmission line problems. Smith charts are essential tools for RF engineers working with transmission lines.
Exam Tip
Smith chart determines = Impedance and SWR. Remember: Smith charts are used to determine impedance and SWR values in transmission lines, design matching networks, and solve transmission line problems.
Memory Aid
"**S**mith **C**hart = **I**mpedance and **S**WR (think 'SC = IS')"
Real-World Application
You measure your antenna impedance as 75 + j25 ohms. You plot this on a Smith chart, then move around the chart to see how the impedance changes as you add transmission line. The chart shows you the SWR (maybe 1.5:1) and helps you design a matching network to transform it to 50 ohms.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Smith charts don't determine beam headings and radiation patterns. Those are antenna pattern measurements, not transmission line impedance analysis.
Option B: Incorrect. Smith charts don't determine satellite azimuth and elevation. Those are pointing calculations, not impedance analysis.
Option D: Incorrect. Smith charts don't determine propagation reliability. They're for impedance and transmission line analysis, not propagation analysis.
题目解析
The correct answer is C: Impedance and SWR values in transmission lines. Smith charts are often used to determine impedance and SWR values in transmission lines. The chart provides a graphical way to solve transmission line impedance problems. Smith charts are the standard tool for transmission line impedance analysis. You can plot an impedance, then move around the chart (representing distance along the transmission line) to see how impedance changes. The chart also shows SWR circles - all points on a constant SWR circle have the same SWR value. This makes it easy to find impedance transformations, calculate SWR, design matching networks, and solve transmission line problems. Smith charts are essential tools for RF engineers working with transmission lines.
考试技巧
Smith chart determines = Impedance and SWR. Remember: Smith charts are used to determine impedance and SWR values in transmission lines, design matching networks, and solve transmission line problems.
记忆口诀
**S**mith **C**hart = **I**mpedance and **S**WR (think 'SC = IS')
实际应用示例
You measure your antenna impedance as 75 + j25 ohms. You plot this on a Smith chart, then move around the chart to see how the impedance changes as you add transmission line. The chart shows you the SWR (maybe 1.5:1) and helps you design a matching network to transform it to 50 ohms.
错误选项分析
Option A: Incorrect. Smith charts don't determine beam headings and radiation patterns. Those are antenna pattern measurements, not transmission line impedance analysis. Option B: Incorrect. Smith charts don't determine satellite azimuth and elevation. Those are pointing calculations, not impedance analysis. Option D: Incorrect. Smith charts don't determine propagation reliability. They're for impedance and transmission line analysis, not propagation analysis.
知识点
Smith chart, Impedance, SWR, Transmission line
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.