Television signal polarization...

Discussion in 'General Electronics Chat' started by Externet, Nov 30, 2015.

  1. Externet

    Thread Starter AAC Fanatic!

    Nov 29, 2005
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  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The polarisation depends on the type of transmission.
    As far as I know the old analog system was horizontal polarized.
    The newer DVB-T is most times vertical polarized.
    As for the antenna types, have a look at the following page:
    http://www.hdtvprimer.com/ANTENNAS/types.html

    Bertus
     
  3. #12

    Expert

    Nov 30, 2010
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    You can derive most of the information you need from looking at a, "normal" TV antenna. Horizontal, hollow tubes. Longer tubes or loops for lower frequencies. Larger diameter tubes for wider bandwidth. More tubes, rods, or disks at some amount of spacing for directivity and amplitude gain. Small diameter, short, solid rods for UHF antennas. The specifics escape me because I always believed $50 to $70 was much more efficient use of my time than learning how to design a broadband receiving antenna...let alone the price of meters to measure the quality of my product!

    Now Bertus comes along and pees in my soup. How am I getting 60 channels of, "digital" TV on the same antenna I installed 30 years ago if they changed the polarization?:mad:
     
  4. ian field

    Distinguished Member

    Oct 27, 2012
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    Whoever transmits the signal, probably publishes technical information which includes polarisation.

    A local aerial installer will know - but probably won't tell you anything that gets you up on the roof instead of him.

    You can always look down the street and see which way up everyone else's aerial is.
     
    Last edited: Nov 30, 2015
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Because polarization is not a brickwall filter, and even the sharpest, narrowest bandwidth design broadens under manufacturing tolerances. And any hunk of metal will pick up *something*. I've never calculated the gain or polarization angle of a coat hanger, but I use one on TV.

    ak
     
    Last edited: Nov 30, 2015
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  6. DickCappels

    Moderator

    Aug 21, 2008
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    In the United States, terrestial television and FM transmissions are transmitted with horizontal polarization (from my reading) because most natural interference was vertically polarized.
     
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  7. SLK001

    Well-Known Member

    Nov 29, 2011
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    US terrestrial DVT broadcasts are either polarized horizontally, circularly or even elliptically. As such, any antenna that could have been use for analog reception will also work well for digital reception. My high gain UHF antennas that did a stellar job of pulling in distant analog signals also does a stellar job of pulling in distant digital signals. And because the signals are digital, the quality of the signal is WAY better (plus they are HD).

    Bertus is in Europe - his broadcasts may indeed be vertically polarized (I believe that European broadcasts can be either vertical or horizontal).
     
    Last edited: Dec 1, 2015
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  8. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    In the UK terrestrial digital tv is broadcast Horizontally for the main transmission, repeater sites use Vertical on a different frequency band so as not to interfere.
     
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