What, in general terms, is standing wave ratio (SWR)?

Standing wave ratio (SWR) is fundamentally a measure of how well a load, such as an antenna, is matched to the transmission line. When an antenna is properly matched to the transmission line, the maximum amount of power is transferred from the transmitter to the antenna, and vice versa. The SWR is determined by the relationship between the voltage standing waves along the transmission line, which is influenced by reflections caused by impedance mismatches.

A SWR of 1:1 indicates an ideal situation where there are no reflections and all transmitted power is successfully radiated by the antenna. As the mismatch increases, the SWR value rises, indicating poor matching and greater voltage standing waves, which can lead to inefficiency and potential damage to the transmitter.

The other choices do not encapsulate the true definition of SWR. For instance, while the ratio of high to low impedance in a feedline relates to impedance matching, it does not specifically quantify the effectiveness of that match in terms of standing waves. Similarly, transmitter efficiency refers to how well the transmitter converts power from a power source into RF energy, and quality of the ground connection is an entirely different aspect of station performance. Each of these concepts is relevant in a broader context, but they don't align with