In what units are the wavelength scales on a Smith chart calibrated?
The correct answer is B: In fractions of transmission line electrical wavelength. The wavelength scales on a Smith chart are calibrated in fractions of transmission line electrical wavelength. These scales show distance along a transmission line in terms of wavelengths.
The Smith chart has wavelength scales around the perimeter that show distance along a transmission line. These scales are calibrated in fractions of electrical wavelength (like 0.0λ, 0.1λ, 0.2λ, etc.). As you move around the chart (representing moving along a transmission line), you can read the distance in wavelengths from these scales. The scales typically go from 0 to 0.5 wavelengths (half a wavelength), since impedance repeats every half-wavelength. These wavelength scales are essential for determining stub lengths and transmission line lengths in matching network design.
Exam Tip
Smith chart wavelength scales = Transmission line electrical wavelength. Remember: Wavelength scales on a Smith chart are calibrated in fractions of transmission line electrical wavelength - they show distance along the line in wavelengths.
Memory Aid
"**S**mith **C**hart **W**avelength **S**cales = **T**ransmission **L**ine **E**lectrical **W**avelength (think 'SCWS = TLEW')"
Real-World Application
You're using a Smith chart to design a matching stub. You move around the chart (representing distance along your transmission line) and read the wavelength scales around the perimeter. The scales show 0.0λ, 0.1λ, 0.2λ, etc. - these tell you how far along the transmission line you are in terms of electrical wavelength.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. The scales aren't in fractions of frequency. They're in fractions of wavelength, not frequency.
Option C: Incorrect. The scales aren't in fractions of antenna electrical wavelength. They're for transmission line wavelength, not antenna wavelength (though they're related).
Option D: Incorrect. The scales aren't in fractions of antenna electrical frequency. They're in fractions of transmission line electrical wavelength.
题目解析
The correct answer is B: In fractions of transmission line electrical wavelength. The wavelength scales on a Smith chart are calibrated in fractions of transmission line electrical wavelength. These scales show distance along a transmission line in terms of wavelengths. The Smith chart has wavelength scales around the perimeter that show distance along a transmission line. These scales are calibrated in fractions of electrical wavelength (like 0.0λ, 0.1λ, 0.2λ, etc.). As you move around the chart (representing moving along a transmission line), you can read the distance in wavelengths from these scales. The scales typically go from 0 to 0.5 wavelengths (half a wavelength), since impedance repeats every half-wavelength. These wavelength scales are essential for determining stub lengths and transmission line lengths in matching network design.
考试技巧
Smith chart wavelength scales = Transmission line electrical wavelength. Remember: Wavelength scales on a Smith chart are calibrated in fractions of transmission line electrical wavelength - they show distance along the line in wavelengths.
记忆口诀
**S**mith **C**hart **W**avelength **S**cales = **T**ransmission **L**ine **E**lectrical **W**avelength (think 'SCWS = TLEW')
实际应用示例
You're using a Smith chart to design a matching stub. You move around the chart (representing distance along your transmission line) and read the wavelength scales around the perimeter. The scales show 0.0λ, 0.1λ, 0.2λ, etc. - these tell you how far along the transmission line you are in terms of electrical wavelength.
错误选项分析
Option A: Incorrect. The scales aren't in fractions of frequency. They're in fractions of wavelength, not frequency. Option C: Incorrect. The scales aren't in fractions of antenna electrical wavelength. They're for transmission line wavelength, not antenna wavelength (though they're related). Option D: Incorrect. The scales aren't in fractions of antenna electrical frequency. They're in fractions of transmission line electrical wavelength.
知识点
Smith chart, Wavelength scales, Transmission line, Electrical wavelength
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.