Ham Radio Extra Class Practice Test 2025 - Free Extra Class License Exam Questions and Study Guide

SWR stands for Standing Wave Ratio, which is a critical parameter in RF engineering. It describes the ratio of the amplitude of standing waves on a transmission line, which occurs when there is a mismatch between the load impedance and the characteristic impedance of the transmission line.

When a radio signal travels down a transmission line and encounters a load that does not perfectly match its impedance, some of the signal is reflected back toward the source. This reflection creates standing waves along the transmission line, and the SWR quantifies the efficiency of power transfer by comparing the voltage of the incident wave to the voltage of the reflected wave. A lower SWR indicates better matching and more efficient power transfer, while a higher SWR can signal potential issues, such as increased losses and possible damage to the transmitter.

Understanding SWR is essential for amateur radio operators to ensure their equipment is functioning effectively and to prevent problems that could arise from poor impedance matching.