Which of these items would be useful for a hidden transmitter hunt?

A hidden transmitter hunt, often referred to as "fox hunting," is a popular amateur radio activity where operators try to locate a concealed radio signal. To find the source of a signal, you need to determine the specific direction from which it is radiating. A directional antenna, such as a Yagi or a loop antenna, is essential for this task because it receives signals much more strongly from one direction than others. By sweeping the antenna and looking for the strongest signal peak (or the deepest "null" where the signal drops out), an operator can track the signal's bearing. An SWR meter and a calibrated noise bridge are incorrect because they are bench or field test instruments used for tuning antennas and checking transmission lines, not for physically locating external signals in the field.