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high frequency always means high quality ?

Discussion in 'The Lounge - Off Topic' started by kobem, Oct 7, 2007.

  1. kobem

    kobem Megabyte Poster

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    i live in Turkey and mostly dsl type of wan service is used , cause already a built telephone
    is available then transmit signals over this line is easy comparing to cable net and other types
    such as satellite net.


    wondering some things making my mind bad by mentioning tv systems:

    before satellite receiver age , there were antennas on each house for tv broadcast and they didn't
    provide high quality however , sometimes , display on tv completely could go.

    with coming digital satellite receiver systems , displays got better and had high quality
    cause signals were coming from satellites to our antennas over high frequency


    and think same thing on cable tv , there are used coaxial cables for transmission
    and also transmitted on high frequency too AND IT GIVES HIGH QUALITY TOO


    .............

    1-thing i have to say is high frequency means always high quality display ?

    digital satellite systems (receiver) have high quality because of LNBs ?

    if so , how it is made in cable tv ?


    2- cable tv uses analog but has HIGH QUALITY but why wasn't this managed on normal antennas
    which enhanced before satellite receiver ?
     
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  2. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    Not always. It *can* mean that, but the quality basicaly comes from how well engineered the system is.
    No - without the LNBs you wouldn't have any signal at all!
    The signal is transmitted down the cable - the quality will depend on the cable and the transmitter and receiver.

    It was. But most people don't put up good aerials, so the quality suffers. With a good aerial you can get good quality.

    In addition - in some counties where the distances are large not enough transmitters were built. Which meant that lots of people were in a fringe area. In the UK lots of transmitters were built, so a good aerial correctly installed gives a good picture.


    Harry. (ex TV engineer)
     
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  3. kobem

    kobem Megabyte Poster

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    .............

    1-thing i have to say is high frequency means always high quality display ?


    Not always. It *can* mean that, but the quality basicaly comes from how well engineered the system is.

    where do we encounter the opposite of this?


    Quote:


    Originally Posted by kobem View Post
    digital satellite systems (receiver) have high quality because of LNBs ?


    No - without the LNBs you wouldn't have any signal at all!
    Quote:


    so because of what ?


    Originally Posted by kobem View Post
    if so , how it is made in cable tv ?


    The signal is transmitted down the cable - the quality will depend on the cable and the transmitter and receiver.




    Quote:


    Originally Posted by kobem View Post
    2- cable tv uses analog but has HIGH QUALITY but why wasn't this managed on normal antennas
    which enhanced before satellite receiver ?


    It was. But most people don't put up good aerials, so the quality suffers. With a good aerial you can get good quality.



    Good aerials , what do you mean with this?


    In addition - in some counties where the distances are large not enough transmitters were built. Which meant that lots of people were in a fringe area. In the UK lots of transmitters were built, so a good aerial correctly installed gives a good picture.


    Harry. (ex TV engineer)
     
    Certifications: CCNA
  4. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    MPEG-4 is a classic case of carefully engineered quality while keeping the bandwidth down.
    You need the LNB to receive the signal and downconvert it.
    Exactly what I said. A bent bit of a wire coathanger doesn't make a good aerial. A double Yagi aerial with high quality low-loss coax download is a lot better!

    Harry.
     
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  5. stuPeas

    stuPeas Megabyte Poster

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    In this case, The Frequency DOESN'T determine the quality DIRECTLY. The higher frequencies for satellite are because the signal NEEDS to be directional. With cable, it is not the fact that the quality is better. Indeed the quality is NOT any better most of the time. It depends on how the TV program is transmitted. If it is transmitted (and made) digitally, the the quality is better. Google "sample rate". Normal TV transmitted signals from a mast tend to loose power because of hills and buildings but if you transmit the signal digitally then you can use technology to correct any lose. This is harder to do with analogue.

    Kobem, This is a WHOLE different topic than you are used to. While i suggest you dont go too deep into it, you should try to get the basics understood, especially the difference between analogue and digital signals. Google "sampling frequency", and maybe "transmission loss". :D
     
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  6. kobem

    kobem Megabyte Poster

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    you said digital signalling provides high quality display but cable tv offers analog signalling
    and it has high quality , how does this occur?
     
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  7. stuPeas

    stuPeas Megabyte Poster

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    Is it high quality??? What do you mean by high quality??? most TV shows look EXACTLY the same to me. It is only a higher quality IF It is HIGH DEFINITION. Also the signal strength IS NOT WEAKENED as much with cable because there are no hills and buildings to absorb the signal.. Did you do the research I said you could do to find the answers?? I'm guessing you did not.
     
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  8. stuPeas

    stuPeas Megabyte Poster

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    There is NO SINGLE ANSWER to this question because it involves a lot of technology consideration (i.e "baseband and Broadband). If you need these answers then you need to understand ALL these considerations, and the reasons they are used for transmitting television signals. I have told you what I can remember, now its time for YOU to do some research ON YOUR OWN.

    Look for the terms "Carrier wave, Frequency modulation, Amplitude modulation, sampling frequency, Baseband, analogue to digital conversion (ADC)"
     
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  9. twizzle

    twizzle Gigabyte Poster

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    One thing to say is that cable Tv no longer offers just analogue (in fact analogue signals are being turned off all over Europe soon) and does transmit Digital just liek satellite.
    High Quality is not the same as High definition. A true High Def Tv has 1080 lines while standard Def has around 526 (from bad memory?) The more lines the better the quality of the Tv can be. Also the Scan rate of the Tv can make a difference, the faster the scan the less flicker in the screen.

    Also the bandwidth and other siganls being sent over the same carrier wave will affect quality.

    Another thing is that TV broadcasters use different equipmenty in the Transmission chain so all have slightly different quality in thier signals. I think DigiTurk have good qulity over in Turkey.

    If you want to know more about TV tranmission technology in depth i'd suggest the BBC's TV technology level 1 course which explains a lot. (though i missed the Explanation of what ASI stream stand for!!)

    And if you do go into TV tech you will need to know things like SDI, SDV, PTS.PCR. ASI, BAndwidths, Field 1 and 2, Interlacing vs Progressive scanning, Multiplexing/Demultiplexing, Transmission standards, DVB and Teletext strandards etc etc etc.... Its a whole different area to IT.
     
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  10. kobem

    kobem Megabyte Poster

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    sorry i wanted to say the tv screen has no artifact no stripes and gives glass-like display
    ( i metioned this by high quality)
     
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