What does an SWR reading of 4:1 indicate?

An SWR (Standing Wave Ratio) reading of 4:1 indicates an impedance mismatch between the transmitter and the antenna system. SWR is a measure of how well the antenna system is matched to the transmission line and the transmitter. A lower SWR value, ideally 1:1, indicates that most of the power sent from the transmitter is being radiated by the antenna, while a higher number signifies that a significant portion of the power is being reflected back, which can happen due to mismatched impedance.

An SWR of 4:1 means that there is a substantial difference between the intended impedance (usually 50 ohms for most transmitters) and the actual impedance presented by the antenna system. This value suggests that the efficiency of the transmission is reduced, as reflected power can cause heat and damage to the transmitter if it operates for extended periods under such conditions.

A reading of 4:1 does not indicate a good impedance match or antenna gain; instead, it identifies a need to adjust the antenna or its feedline to achieve better matching and improve performance.