What is standing wave ratio (SWR)?

• A. A measure of transmitted power
• B. A measure of load impedance
• C. A measure of how well a load is matched to a transmission line
• D. A measure of voltage levels in the line

Answer: (C)

Standing wave ratio (SWR) is defined as a measure of how well a load is matched to a transmission line. This concept is crucial for anyone operating in radio frequencies, as it directly affects the efficiency of power transfer from the transmitter to the antenna. When the load impedance (e.g., the antenna) is well-matched to the transmission line’s characteristic impedance, the SWR will be at its lowest, ideally around 1:1. This indicates that the maximum amount of power is being transferred without excessive reflections.

When there is a mismatch, reflected waves occur, leading to an increase in SWR. A high SWR indicates that there is a significant amount of power being reflected back towards the transmitter, which can lead to inefficiencies and potential damage to the transmitter. Understanding SWR allows operators to adjust their systems for optimal performance, by ensuring that their antennas are correctly tuned to match the length and impedance of their transmission lines.

This understanding emphasizes the importance of good impedance matching in radio communications, which results in effective transmission and reduced risk of damage to equipment. While the other options cover related concepts, they do not directly define SWR.