Operation Manual

Niagara SCX User Guide
ViewCast 121
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.
Because 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 102) information about only the chrominance (coloring) portion
of the video signal. It does not respond to other parts of the video signal.
Figure 102. Vectorscope Display
Two important parameters of the chrominance signal exist that may suffer distortions leading to
noticeable picture problems.
 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.
The processing within a vectorscope and the display of the processed signals readily detects and
evaluates both phase and gain distortions of the chrominance.