Why is an oscilloscope used in radio testing?

An oscilloscope is a crucial tool in radio testing because it allows engineers and technicians to visualize and analyze the voltage waveforms of electrical signals in real time. By displaying these waveforms on a screen, users can observe various characteristics of the signal, such as its amplitude, frequency, and shape. This ability to see the signal helps in troubleshooting and ensuring that the radio equipment operates within the intended specifications.

When working with radio frequencies, it is essential to confirm that the signals are being transmitted and received correctly. The oscilloscope can display modulation types in amplitude and frequency modulation, making it invaluable for developing and testing transmission systems. Its capability to provide a detailed view of signal distortions or failures directly supports the maintenance of high-quality communication systems.

The other options, while related to audio and electrical diagnostics in some manner, lack the specific focus on the detailed analysis of voltage waveforms that an oscilloscope provides. Thus, the oscilloscope's primary function in the context of radio testing is indeed to visualize and measure voltage waveforms, which is why this answer is accurate.