analogue tv signal synchronisation.

Discussion in 'Wireless & RF Design' started by ANICETH, Feb 28, 2016.

  1. ANICETH

    Thread Starter New Member

    Feb 21, 2016
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    Hi there!!..
    I have a problem with the analogue tv signal synchronization on the purpose of the vertical and horizontal synchronization in the image creation on the screen and what happens to an image when these two synchronization schemes are interchanged.
     
  2. crutschow

    Expert

    Mar 14, 2008
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    This may help you understand the analog TV synchronization process.

    I don't understand what you mean by: what happens if the two synchronization schemes are interchanged?
    There is one scheme that has separate horizontal and vertical sync pulses.
     
  3. ANICETH

    Thread Starter New Member

    Feb 21, 2016
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    I mean that if the vertical sync pulse is put on the horizontal syn pulse and vise versa. What will happen to the image formation on the screen?
     
  4. DickCappels

    Moderator

    Aug 21, 2008
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    If your monitor is well designed, nothing will happen. If it is poorly designed flat panel display you will probably get garbage. If it is a poorly designed CRT display you might destroy the horizontal output stage.
     
  5. crutschow

    Expert

    Mar 14, 2008
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    Why would you want to do that? :confused:
    It makes no sense.
     
  6. recklessrog

    Member

    May 23, 2013
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    That is a nonsense question.
     
  7. DickCappels

    Moderator

    Aug 21, 2008
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    The question makes sense, because it can happen (and used to in the days of separate coax cables for each component). Doing is intentionally may not be rational unless one thought there might be some use or benefit from doing so.
     
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  8. BR-549

    Well-Known Member

    Sep 22, 2013
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    If you switch the sync signals, and the syncs have the same frequency gain with the circuits and coils, you would get a vertical raster instead of a horizontal one.

    A sideways image.

    Of course the syncs don't have the same bandpass. You could rotate the yoke 90 degrees, but you would have to touch up screen size adjustments, because the screen is not square.

    That's what would happen.
     
  9. ANICETH

    Thread Starter New Member

    Feb 21, 2016
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    I am a little bit understanding you on this. thank you let's go on brainstorming. I was asked this question by my Professor on TV signals.
     
  10. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    It doesn't mention that there are *four* color fields in a frame, but overall an ***excellent*** summary.

    ak
     
  11. crutschow

    Expert

    Mar 14, 2008
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    There are three colors, RGB, in the chrominance and the B&W luminance.
    What's the fourth color you are referring to? :confused:
     
  12. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Not colors, color fields.

    In the same way there are two monochrome fields interlaced into a monochrome frame, there are two color fields interlaced into each monochrome field. This falls out of the line rate math. There are 525 lines per frame, or 262.5 lines per field. The half-line is critical to the monochrome interlace timing. In the same way, there are 227.5 cycles of subcarrier per line, so the 1/2 line per field means 1/4 cycle of subcarrier per field. No one cares about this except for some poor bastard designing an electronic editor for NTSC videotape. For perfect edits of a monochrome signal, where the vertical sync phase doesn't jump at the edit point, edits can happen only on frame boundaries, not field boundaries. Otherwise, there might be two odd fields in series across an edit point. This would cause a momentary jump in the picture at the receiver, or at worst a single vertical roll, but it is a real problem for the mechanical servos in a videotape machine. For perfect color edits, where the color subcarrier is perfectly in phase across the edit point, edits can happen only every other mono frame. This limits the overall edit "resolution" to 14.985 Hz, 1/4 of the monochrome field rate of 59.94 Hz.

    ak

    Yes, I was that poor bastard, working nights at work-study wages. Technically, not a bastard but definitely poor.
     
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