Practical takeaway
The Smith chart is a graphical calculator for complex impedance and admittance on transmission lines. It becomes much easier when treated as a map of reflection coefficient.
E9G · Amateur Extra question group
Smith Chart
The Smith chart is a graphical calculator for complex impedance and admittance on transmission lines. It becomes much easier when treated as a map of reflection coefficient.
Amateur Extra exam focus
The explanation below teaches the ideas behind E9G while keeping the important terms recognizable. The Quiz Me button uses the current question-pool wording for this group.
1. The center is a perfect match
The chart is normalized to the line impedance. The center represents normalized impedance 1 + j0, meaning the load equals characteristic impedance and reflection coefficient is zero.
2. Moving along a line rotates around the chart
Changing line length does not change reflection magnitude on an ideal lossless line; it changes reflection phase. On the Smith chart that appears as motion around a constant-SWR circle.
3. Impedance and admittance are opposite points
A 180-degree rotation around the chart center converts a normalized impedance to the corresponding normalized admittance, which simplifies series and shunt matching problems.
E9G checklist
- Chart center represents a matched load.
- Constant-SWR circles represent constant reflection magnitude.
- Line length moves the impedance around a constant-SWR circle on an ideal line.
- Impedance and corresponding admittance are 180 degrees apart on the chart.
Exam scope: NCVEC 2024-2028 Amateur Extra Class (Element 4), effective July 1, 2024 through June 30, 2028, with February 4, 2026 fourth errata. The current NCVEC pool is the exam authority; explanatory prose here is SPARKA teaching material. NCVEC pool