Which of the following is used to determine if an antenna is resonant at the desired operating frequency?
Why An antenna analyzer sweeps a small signal across a range of frequencies and reports SWR and impedance at each point, so you can see where the SWR dips to its minimum. That dip marks the resonant frequency, where the antenna's reactance is near zero and it presents mostly resistance. If the dip is above or below your band, the analyzer tells you to shorten or lengthen the antenna.
Watch out A frequency counter only measures the frequency of a signal fed into it, it tells you nothing about how the antenna is behaving at that frequency. A VTVM is an old-style voltmeter and a Q meter measures the quality factor of coils and capacitors on the bench.
Analyzer = SWR versus frequency curve. Find the dip, find resonance.