Sinewave

Although, in response to changing U and V values, the chroma sinewave changes phase with respect to the subcarrier, it's not correct to say that the subcarrier is simply "phase modulated".

Given a sinewave generator of very low inherent distortion, it can be used as input to amplification equipment, whose distortion at different frequencies and signal levels can be measured by examining the output waveform.

In a modem, these may be sinewave tones with unique combinations of amplitude, phase and/or frequency.

Spectral purity The sinewave output of an ideal oscillator is a single line in the frequency spectrum.