Subelement L: L – Installation, Maintenance & Repair— Topic 75: Test Equipment
Question 3-75L6
Element 3 (GROL)Which of the following contains a multirange AF voltmeter calibrated in dB and a sharp, internal 1000 Hz bandstop filter, both used in conjunction with each other to perform quieting tests?
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.
Related Questions
3-75L4 On an analog wattmeter, what part of the scale is most accurate and how much does that accuracy extend to the rest of the reading scale?3-75L5 Which of the following frequency standards is used as a time base standard by field technicians?3-76L1 What is used to decrease circuit loading when using an oscilloscope?3-76L2 How does a spectrum analyzer differ from a conventional oscilloscope?3-76L3 What stage determines the maximum frequency response of an oscilloscope?