Deep Dive: E9G06
The correct answer is B: Reactance axis. On the Smith chart shown in Figure E9-3, the large outer circle on which the reactance arcs terminate is called the reactance axis. This is the outer boundary of the chart where all reactance values are plotted. The reactance axis is the outer circle of the Smith chart. All reactance arcs (both inductive and capacitive) terminate on this outer circle. The reactance axis represents infinite resistance - any point on this outer circle has infinite resistance with some reactance value. The chart is bounded by this reactance axis, which forms the outer perimeter. This is a fundamental feature of the Smith chart structure - the reactance axis is where all the reactance arcs end.
Why Other Answers Are Wrong
Option A: Incorrect. The prime axis is the horizontal line through the center (representing pure resistance), not the outer circle. Option C: Incorrect. The resistance axis is the horizontal line through the center, not the outer circle. Option D: Incorrect. The impedance axis isn't a standard term. The outer circle is the reactance axis.
Exam Tip
Smith chart outer circle = Reactance axis. Remember: The large outer circle on which reactance arcs terminate is called the reactance axis - it represents infinite resistance with various reactance values.
Memory Aid
**O**uter **C**ircle = **R**eactance **A**xis (think 'OC = RA')
Real-World Example
You look at a Smith chart. The outer boundary is a large circle - this is the reactance axis. All the reactance arcs (both inductive in the upper half and capacitive in the lower half) terminate on this outer circle. Points on this circle have infinite resistance with some reactance value.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E9G
Reference: FCC Part 97.3
Key Concepts
Official Pool Source
Question text and answer key are synchronized with the current NCVEC Extra Class pool and mapped to the E9G topic.