Deep Dive: T9B12
The correct answer is A: A measure of how well a load is matched to a transmission line. Standing Wave Ratio (SWR) is a measure of how well a load is matched to a transmission line. SWR indicates the ratio of maximum to minimum voltage (or current) on a transmission line, which reflects how well the antenna impedance matches the feed line impedance. A 1:1 SWR means perfect match, higher SWR means mismatch. For amateur radio operators, SWR is the primary indicator of antenna system performance and impedance matching. Understanding SWR helps diagnose antenna and feed line problems.
Why Other Answers Are Wrong
Option B: Incorrect. SWR isn't the ratio of amplifier power output to input - that's amplifier efficiency. SWR measures impedance matching, not power ratios. Option C: Incorrect. SWR isn't transmitter efficiency ratio - efficiency is output power divided by input power. SWR is about impedance matching. Option D: Incorrect. SWR isn't an indication of ground connection quality - ground affects other things, but SWR measures impedance matching between feed line and antenna.
Exam Tip
SWR = measure of load matching to transmission line. Think 'S'WR = 'S'tanding 'W'ave 'R'atio = 'S'hows 'W'ell 'R'adiator matches. Measures how well antenna impedance matches feed line. Not about amplifier efficiency, transmitter efficiency, or ground quality.
Memory Aid
SWR = measure of load matching. Think 'S'WR = 'S'tanding 'W'ave 'R'atio = 'S'hows 'W'ell 'R'adiator matches. Measures impedance matching between antenna and feed line. Lower is better (1:1 is perfect).
Real-World Example
You measure SWR on your antenna system. A 1:1 reading means your antenna presents exactly 50 ohms to the feed line - perfect match. A 3:1 reading means significant mismatch - the antenna impedance doesn't match the 50-ohm feed line well. SWR tells you how well matched your system is.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T9B
Reference: 2022-2026 Question Pool · T9 - Antennas and feed lines
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T9B topic.