What instrument may be used to verify proper radio antenna functioning?

An SWR (Standing Wave Ratio) meter is essential for verifying proper radio antenna functioning because it measures the efficiency of the antenna system. When a radio frequency signal is transmitted through an antenna, some of the energy is radiated into space while some may reflect back towards the transmitter if the antenna is not properly matched to the transmission line. The SWR meter provides a ratio of the forward power sent to the antenna versus the reflected power. A low SWR indicates that most of the transmitted power is effectively radiated, signifying that the antenna is well-matched and functioning correctly. High SWR values suggest that there may be an issue, such as impedance mismatch, which could lead to reduced performance or damage to the transmitter.

In contrast, other instruments serve different purposes. A frequency counter measures the frequency of the signal being transmitted but does not assess antenna performance directly. A power meter measures the actual power output from the transmitter, which can give some insights but does not specifically address how well the antenna is radiating that power. A field strength meter measures the strength of the radio waves in a specific location, which can indicate antenna performance indirectly but does not provide direct measurements of reflection or matching as the SWR meter does.