The device used to measure FM, AM, and single-sideband signals in an application, such as a mobile communications system, is a(n) _____.

The appropriate device for measuring FM, AM, and single-sideband signals, particularly in contexts like mobile communications systems, is an RF field strength analyzer. This instrument is specifically designed to assess the strength and quality of radio frequency signals, making it highly suitable for analyzing the characteristics of different modulation types such as Frequency Modulation (FM), Amplitude Modulation (AM), and Single-Sideband (SSB) signals.

RF field strength analyzers can measure various parameters, including signal amplitude, frequency, and modulation type, which are critical aspects in mobile communications where maintaining signal integrity is essential for effective communication. They often provide real-time analysis, helping technicians and engineers optimize system performance.

While oscilloscopes can display signals and allow for visual analysis of waveforms, they are not specifically tailored for RF measurements and may lack the sensitivity needed for accurate modulation type analysis in a mobile communications context. Signal generators are used to produce signals of specified frequencies and amplitudes but do not measure signals. Network analyzers primarily focus on the network characteristics of RF components, such as impedance and return loss, rather than direct signal modulation analysis. Thus, the RF field strength analyzer stands out as the most relevant and specialized choice for the purpose described.