Re: What can you do with a Waveform Monitor or Vector Scope, other than TV measurements?
Don Black <donald_black@...>
Fred,toggle quoted messageShow quoted text
The NTSC and PAL color systems encode the two chroma signals on the color oscillator in quadrature (90 degrees phase difference). Then a phase sensitive detector in the receiver is able to recover both signals, not just in amplitude but polarity. The resultant mixed signals can have any magnitude or phase (referenced to the main oscillator). In the receiver the local color oscillator is phase locked to the modulator by the sample color burst signal during horizontal blanking when there's no signal (at the end of each scanned line while waiting for the trace to return for the next line scan). The familiar color bar test signal includes all the three primary colors (red, green blue) and their combinations as a standard test signal. The resulting chroma signal has these colors as standard values, both amplitude and phase for each color. A Vectorscope displays the signal in both amplitude and phase so any errors in either are readily apparent. In effect the Vectorscope is a color receiver that plots the chroma signal as X and Y co-ordinates to produce the polar response. The PAL signal is a variant of the original NTSC standards that reverses the phase of one signal by 180 degrees on each alternate line (PAL is Phase Alternate Line). this allows great error correction in the receiver, somewhat optically where there's no electronic correction but in all modern PAL sets it's done electronically very effectively.
On 19-Jul-13 7:12 PM, Pa4tim wrote: