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Niagara SCX User Guide
ViewCast 93
Chapter 12: Tuning Utilities
Some electrical signals convey television pictures. Cables then carry this video signal from one place
to another. Along the way, the signal may pass through various pieces of equipment such as video
tape machines, switchers, character generators, special effects generators, and transmitters. Any of
this equipment can change or distort the signal in undesirable ways.
Since signal quality acts as a major determining factor for picture quality, you need to be able to
detect and correct any signal distortions. The signal must be correct before the picture can be correct.
You can use a waveform monitor to measure luminance or picture brightness as well as a high
frequency color signal called chrominance. You require an instrument called a vectorscope to
control quality of video chrominance (coloring) especially in more complex systems.
Vectorscope
A vectorscope displays (Figure 150) information about only the chrominance (coloring) portion of
the video signal. It does not respond to other parts of the video signal.
Figure 150. Vectorscope Display
Two important parameters of the chrominance signal that may suffer distortions leading to
noticeable picture problems exist.
Table 24. Chrominance Signal Parameters
Parameter Description
Amplitude Gain and phase (timing). Amplitude, an independent measurement, you
can actually make with a waveform monitor.
Phase The relationship between the two signals. In this case, the relationship
between the chrominance signal and reference burst on the video.