Which of the following is used to determine if an antenna is resonant at the desired operating frequency?

An antenna analyzer is a specialized piece of test equipment used to measure various characteristics of an antenna system, including its resonant frequency and Standing Wave Ratio (SWR). By sweeping across a range of frequencies, it easily shows where the antenna performs best. When an antenna is resonant, its impedance is primarily resistive, and it accepts RF power most efficiently. The antenna analyzer contains a small built-in signal generator, allowing you to check resonance without ever needing to transmit a high-power signal from your radio. While a frequency counter measures the frequency of an oscillating signal, and a VTVM measures voltage, neither can directly measure an antenna's resonance. Therefore, the antenna analyzer is the correct, purpose-built tool for this job.