During a two-tone linearity test of an SSB transmitter, which instrument is commonly used to view the output waveform?

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Multiple Choice

During a two-tone linearity test of an SSB transmitter, which instrument is commonly used to view the output waveform?

The key idea is to observe the signal in the time domain to detect how the two input tones are reproduced by the transmitter. An oscilloscope lets you see the actual output waveform as it evolves over time, so you can tell whether the two sine waves are being reproduced cleanly or if nonlinearities are adding distortion. With two tones, a perfectly linear transmitter would output a sum of the two sine waves without extra shapes or clipping. On the scope this appears as a smooth, unchanged waveform that reflects those two tones. If the stages ahead of the RF output are nonlinear, the waveform will distort—flattening peaks, bending the curve, or showing irregularities—indicating intermodulation or other distortion products caused by nonlinearity. Spectrum analyzers, by contrast, show the frequency content (intermodulation products) but not how the waveform looks in time. Wattmeters measure power, not the waveform shape, and frequency counters measure frequency, not waveform. So the oscilloscope is the tool that provides the direct view of the output waveform needed for assessing linearity with a two-tone test.

The key idea is to observe the signal in the time domain to detect how the two input tones are reproduced by the transmitter. An oscilloscope lets you see the actual output waveform as it evolves over time, so you can tell whether the two sine waves are being reproduced cleanly or if nonlinearities are adding distortion.

With two tones, a perfectly linear transmitter would output a sum of the two sine waves without extra shapes or clipping. On the scope this appears as a smooth, unchanged waveform that reflects those two tones. If the stages ahead of the RF output are nonlinear, the waveform will distort—flattening peaks, bending the curve, or showing irregularities—indicating intermodulation or other distortion products caused by nonlinearity.

Spectrum analyzers, by contrast, show the frequency content (intermodulation products) but not how the waveform looks in time. Wattmeters measure power, not the waveform shape, and frequency counters measure frequency, not waveform. So the oscilloscope is the tool that provides the direct view of the output waveform needed for assessing linearity with a two-tone test.

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