What is the primary use of a spectrum analyzer?

• A. Detects RF spectrum
• B. Measures voltage and resistance
• C. Displays time-domain waveforms
• D. Shows signal strength

Answer: (D)

The main idea being tested is how a spectrum analyzer is used in RF analysis. A spectrum analyzer renders the amplitude of signals as a function of frequency, giving you a spectrum. This means you can see how strong each frequency component is, identify where signals are occupying bandwidth, spot spurs or unwanted emissions, and gauge the overall noise floor. That ability to quantify signal strength across the frequency range is what makes the spectrum analyzer a core tool for understanding the spectral content of a signal.

It’s not primarily about measuring DC parameters like voltage or resistance, nor about displaying time-domain waveforms—that’s the domain of other instruments. While it does reveal whether signals are present at various frequencies, its defining value is showing how strong those signals are across the spectrum, which is exactly what the graph of signal strength versus frequency provides.