Explanation: A SINAD (Signal-to-Noise And Distortion) meter is specifically designed for receiver sensitivity measurements, also known as quieting tests. It functions by injecting a standard audio tone (commonly 1000 Hz) into the receiver. The meter then measures the output audio level. To isolate the noise and distortion, the meter employs a sharp, internal 1000 Hz bandstop filter that removes the original test tone from the receiver's output. The remaining signal, representing noise and distortion, is then measured by a multirange AF voltmeter, calibrated in dB, to determine the SINAD ratio. A reflectometer measures SWR, a dip meter finds resonant frequencies, and a vector-impedance meter analyzes complex impedance; none of these devices are equipped with the specific audio filtering and dB-calibrated AF voltmeter needed for quieting tests.