What type of coordinate system is used in a Smith chart?
The correct answer is B: Resistance circles and reactance arcs. A Smith chart uses a resistance circles and reactance arcs coordinate system. The chart is a circular graph with constant resistance circles and constant reactance arcs.
The Smith chart has two families of curves: circles of constant resistance (horizontal circles) and arcs of constant reactance (curved arcs). Resistance circles are centered on the horizontal axis, with values from 0 (left edge) to infinity (right edge). Reactance arcs are curved lines representing inductive (upper half) and capacitive (lower half) reactance. Together, these circles and arcs form a grid where any impedance can be plotted as a point. The intersection of a resistance circle and a reactance arc gives you the impedance value.
Exam Tip
Smith chart coordinates = Resistance circles and reactance arcs. Remember: Smith charts use resistance circles (constant resistance) and reactance arcs (constant reactance) as the coordinate system.
Memory Aid
"**S**mith **C**hart = **R**esistance **C**ircles + **R**eactance **A**rcs (think 'SC = RC+RA')"
Real-World Application
You're using a Smith chart. You see circles representing constant resistance (maybe 25, 50, 100 ohms) and curved arcs representing constant reactance (maybe +j50, -j50 ohms). To plot an impedance like 50 + j25, you find the 50-ohm resistance circle and the +j25-ohm reactance arc, and their intersection is your impedance point.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Smith charts don't use voltage circles and current arcs. They use resistance circles and reactance arcs.
Option C: Incorrect. Smith charts don't use voltage chords and current chords. The coordinate system is resistance circles and reactance arcs.
Option D: Incorrect. Smith charts don't use resistance lines and reactance chords. They use circles (for resistance) and arcs (for reactance).
题目解析
The correct answer is B: Resistance circles and reactance arcs. A Smith chart uses a resistance circles and reactance arcs coordinate system. The chart is a circular graph with constant resistance circles and constant reactance arcs. The Smith chart has two families of curves: circles of constant resistance (horizontal circles) and arcs of constant reactance (curved arcs). Resistance circles are centered on the horizontal axis, with values from 0 (left edge) to infinity (right edge). Reactance arcs are curved lines representing inductive (upper half) and capacitive (lower half) reactance. Together, these circles and arcs form a grid where any impedance can be plotted as a point. The intersection of a resistance circle and a reactance arc gives you the impedance value.
考试技巧
Smith chart coordinates = Resistance circles and reactance arcs. Remember: Smith charts use resistance circles (constant resistance) and reactance arcs (constant reactance) as the coordinate system.
记忆口诀
**S**mith **C**hart = **R**esistance **C**ircles + **R**eactance **A**rcs (think 'SC = RC+RA')
实际应用示例
You're using a Smith chart. You see circles representing constant resistance (maybe 25, 50, 100 ohms) and curved arcs representing constant reactance (maybe +j50, -j50 ohms). To plot an impedance like 50 + j25, you find the 50-ohm resistance circle and the +j25-ohm reactance arc, and their intersection is your impedance point.
错误选项分析
Option A: Incorrect. Smith charts don't use voltage circles and current arcs. They use resistance circles and reactance arcs. Option C: Incorrect. Smith charts don't use voltage chords and current chords. The coordinate system is resistance circles and reactance arcs. Option D: Incorrect. Smith charts don't use resistance lines and reactance chords. They use circles (for resistance) and arcs (for reactance).
知识点
Smith chart, Resistance circles, Reactance arcs, Coordinate system
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.