Basics of Smith Charts - QSL.net

Basics of Smith Charts

Alan Wolke ? W2AEW ARRL NNJ Technical Coordinator



W2AEW

What is a Smith Chart

? A graphical tool to plot and compute:

? Complex impedance ? Complex reflection coefficient ? VSWR ? Transmission line effects ? Matching networks ? ...and more

? Let's break it down....

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W2AEW

Normalized Impedance

? Normalized Z = Actual Z / System Z0

? For Z0=50, divide values by 50

? Example:

? = 37 + 55

?

=

37 50

+

55 50

? = 0.74 + 1.10

This is what we plot on the chart

? Makes it usable for any system Z0

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W2AEW

Z Regions on the Smith Chart

+

+j Inductive

Purely Resistive = 0

- -j Capacitive

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W2AEW

Key Values on the chart

Short Circuit

Z0

(system impedance)

Open Circuit

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