Why is video inverted for transmission?

Discussion in 'Digital Photography' started by Green Xenon [Radium], Sep 20, 2007.

  1. Green Xenon [Radium]

    Jerry Avins Guest

    Randy Yates wrote:

    ...
    Horizontal sync occurs at the horizontal scan rate, if that's what you
    mean. A pulse can *have* a rate, but it can't *be* one. There are
    vertical sync pulses too; those come at the vertical rate. During
    vertical retrace, the horizontal oscillator needs to skip or add half a
    line.

    ...

    Jerry
     
    Jerry Avins, Sep 24, 2007
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  2. GADS
    I think my Father could top your stories.

    He told of making capacitors.
    The rule of thumb was "1 micro farad" / "gallon of 'fish tank' "

    He also apparently operated a _legal_ land based spark gap transmitter.
    [I was once challenged on that statement - Checking with rep of Antique
    Wireless Association of Holcomb NY showed claim was _feasible_.]
     
    Richard Owlett, Sep 25, 2007
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  3. Jerry Avins wrote:

    (snip)
    Lead gives a yellow tint. I have seen lead-glass bricks used for
    radiation shielding that you can see through. They might be more
    than 50% lead by weight and only a light yellow color.

    There are other requirements for a CRT, though.

    -- glen
     
    glen herrmannsfeldt, Sep 25, 2007
  4. Michael A. Terrell wrote:

    (snip)
    I used to have an oscilloscope built out of a WWII radar
    receiver.

    -- glen
     
    glen herrmannsfeldt, Sep 25, 2007
  5. Don Pearce wrote:

    (snip)
    I don't see why the colors couldn't be right. Resolution is
    a complicated question. Also, fast changing scenes may be
    too much for the available bit rate.

    -- glen
     
    glen herrmannsfeldt, Sep 25, 2007
  6. Green Xenon [Radium]

    Joel Kolstad Guest

    Absolutely... something a lot of people don't realize is that spark-gap
    transmitters did have resonant circuits almost immediately after the first few
    were built. Heck, strictly speaking I don't believe there's anything
    inherently illegal about a spark-gap transmitter today -- it'd just that you'd
    probably have to filter the daylights out of it to meet mordern emission
    standards, so it wouldn't exactly be an "authentic" setup.
     
    Joel Kolstad, Sep 25, 2007
  7. Green Xenon [Radium]

    Joel Kolstad Guest

    He's probably complaining about how -- somewhat ironically -- as technology
    advances and becomes easier to use, those using it tend to be less educated
    and therefore more likely to get something wrong (such as colors)! Perhaps
    the relevant example here was the "wall of CRTs" seen in big box stores before
    LCDs/plasma displays took over -- inevitably they were all cranked up so
    bright to "look good" that there was pretty bad geometric distortion,
    blooming, and awful color rendition. But the average consumer cared about
    little more than brightness, it would seem, and voted with their wallet
    accordingly...
     
    Joel Kolstad, Sep 25, 2007
  8. Green Xenon [Radium]

    Frank ess Guest

    Ayuh.

    --
    Frank ess

    Forecasting is difficult.
    Particularly about the Future.
    —Deepak Gupta
     
    Frank ess, Sep 25, 2007
  9. Randy Yates wrote:
    (snip)
    How many vacuum tubes does it take to build a PLL?

    -- glen
     
    glen herrmannsfeldt, Sep 25, 2007
  10. Jerry Avins wrote:

    (snip)
    Some years ago I had the book "Television To-day and To-morrow"
    from the Caltech library. It was written in 1930. There were
    descriptions of spinning disks and neon lamps. No CRTs.

    It wasn't useful for questions about the color subcarrier,
    the reason I went looking in the first place.

    http://clas.caltech.edu/record=b1018287

    -- glen
     
    glen herrmannsfeldt, Sep 25, 2007
  11. Green Xenon [Radium]

    Al in Dallas Guest

    Or lack thereof.
     
    Al in Dallas, Sep 25, 2007
  12. Green Xenon [Radium]

    Al in Dallas Guest

    My cable provider has claimed that the digital artifacts that I've
    seen are due to squirrels chewing on cables and as soon as they get
    around to replacing the lines, the artifacts should go away.
     
    Al in Dallas, Sep 25, 2007

  13. I don't watch that crap. Basically, it's local and national news,
    and about 10 hours a week of the Sci-Fi channel for a little escapism.
    I listen to radio more than I watch TV. Still, after being an engineer
    at three TV stations it has become ingrained to insist on quality. If
    you have ever seen NTSC video on a $7,000 RGB studio monitor, fed from
    a $100,000 studio camera and lens, you would puke at the digital TV
    crap. I have seen it in Circuit City and Best Buy. I already have
    problems with analog TV, because Brighthouse's digital to analog
    converters are always freezing the video with a garbage display, and a
    loud roar from the speakers for several seconds at a time.

    I was given a two year old 32" Sony HDTV 'Capable' TV a few weeks
    ago, and have no idea what I'm going to do with it. I have considered
    converting it to a computer monitor.


    You can blame the cheap ass networks who switched to KU band digital
    feeds with barely enough bandwidth to supply a fixed image without
    problems. After they piggyback all the control and timing data, its no
    wonder the system freezes.


    None of the stations I worked at broadcast that crap. One was
    military, and the other two were Christian TV stations. In fact, they
    didn't even have commercials.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
    Michael A. Terrell, Sep 25, 2007

  14. Some of the tube design guides from the manufacturers warned you not
    to use any N/C pins, because they may be used in the future.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
    Michael A. Terrell, Sep 25, 2007

  15. My high school's Physic department had the entire RADAR system, with
    manuals. It had been in storage since it was declassified, and they
    finally decided to try to return it to the government. They were told
    to destroy it, so it was sent to the electronics class to be parted
    out. I managed to grab the receiver case, and the transmitter before it
    was parted out. I had the 15E and 15R Eimac tubes that were designed
    for that RADAR transmitter, but I don't know if I still have them.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
    Michael A. Terrell, Sep 25, 2007

  16. Squirrels do chew hardline, till they hit the 60 V squared wave 30 A
    supply. That doesn't mean that they are full of crap. If you can find a
    damaged spot they haven't repaired, report them to the FCC for radiation
    problems. They will fix it, or be shut down.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
    Michael A. Terrell, Sep 25, 2007

  17. that's really strange, too. 30 years ago, when I worked in a TV shop
    that sold TVs, people bought the one with the best picture. A lot of
    them watched TV in a semi darkened room, and didn't want them to be
    blindingly bright. Now, they want to watch them outdoors, in the noon
    day sun.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
    Michael A. Terrell, Sep 25, 2007

  18. More important: How many tons of air conditioning can you afford to
    run 24/7?

    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
    Michael A. Terrell, Sep 25, 2007
  19. You'll probably find that your Sony is limited to WXGA (1366x768).
    Check the specs. WXGA is ok, but is nowhere near what can be done
    with a "real" 32" LCD computah monitor. For example, an HP LP3065 30"
    monitor will do WQXGA (2560x1600) or roughly twice the number of
    pixels.
    DTV compression levels were established by cranking up the compression
    until the complaints rolled in on the support phone numbers. I also
    went through that exercise with CATV. Cramming extra channels into
    the pipe is worth lots of money. What we have today is "adequate"
    picture quality that paying customers can afford. There may be a
    market for high quality broadcast video, but the GUM (great unwashed
    masses) prefer cheap. So, we get maximally compressed video of
    minimal quality. I don't like it, but my DirecTV subscription is
    affordable, so I'll tolerate the loss in quality.
     
    Jeff Liebermann, Sep 25, 2007
  20. Green Xenon [Radium]

    Arny Krueger Guest

    I think that a smple PLL might be done with 3 multi-section tubes. A
    dual-diode for the phase detector, two tubes or a triode/pentode the VCO,
    and a dual-triode for the op amp. Add more if you were trying to do
    frequency division or multiplcation at the same time.
     
    Arny Krueger, Sep 25, 2007
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