Re: What can you do with a Waveform Monitor or Vector Scope, other than TV measurements?


Don Black <donald_black@...>
 

Fred,
        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.

Don Black.

On 19-Jul-13 7:12 PM, Pa4tim wrote:
 
Interesting, I got some for free a year or to ago, but never used them.  Can not find much about them, probably ome semi-custom things because they also have non-tek colors. One was a waveform monitor, One was a vector display, it looked like a polar diagram so I was happy, I wanted to use it for my HP VNA ( I know nothing about Video and the guy who gave them either, and we did not have a clue about what they were used for, HP had a polar display for that VNA so i hoped this was an equivalent from Tek, but then I find out they were for video) The 3rd is a big orange XY diplay ( no typenumber, it comes out of a medical instrument) and I use that for a noise/gain analyser. 

Fred PA4TIM

Op 19 jul. 2013 om 09:35 heeft "cheater00 ." <cheater00@...> het volgende geschreven:

 

Hi guys,
there are many cheap Waveform Monitors and Vector Scopes around, and -
given that their main use is utterly obsolete, because nobody uses PAL
or NTSC anymore or will stop using it soon - are there other uses for
those units that a layperson such as myself wouldn't know about? Can
they somehow be used as more general instruments? Do some of them at
least yield parts useful in other equipment?

Thanks,
Damian


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