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Lnb Upgrade ?

Discussion in 'Satellite TV, Sky TV & FreeSat' started by Steve N, Mar 17, 2005.

  1. Steve N

    Steve N
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    Is it worth changing my LNB on my motorised dish. Would one of the expensive ones help prevent some of the blocking effects I get during fast moving scenes.
    My local installer seems to think they are all the same
    Mags like What Sat don't seem to review LNB's
    All commments and advice welcome
     
  2. Chris Muriel

    Chris Muriel
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    Unlikely to make any significant difference.
    I was trained/educated as an RF/Communications engineer so , unlike Joe Public , I know how NF should correctly be measured and specified - for use in link budgets with Friis equations.

    Consumer LNB noise figures are more marketing than anything else (specs are typical not maximum and best figure will only apply at 1 spot frequency).
    OTOH a larger dish (which gives more NOISE FREE gain) will help.

    Chris Muriel, Manchester
     
  3. Steve N

    Steve N
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    Thanks Chris
     
  4. bcl

    bcl
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    Hi, Steve,

    I don't think a new lnb will help the problem.

    The blocking you see is due to automatic bitrate limiting on the satellite up-link. To get as many channels as possible on the satellite's transmitter, bitrate has to be restricted. Fast changing scenes have high bitrates. a stationary picture has minimum bitrate until it is changed. So fast pans on sport or flashing lights stand a good chance of blocking. Accountants v. engineering!
     
  5. Chris Muriel

    Chris Muriel
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    Yes "Accountants v. engineering!" .

    I would call it an inevitable and undesirable by product of statistical multiplexing (which is what you described).


    If all channels in a multiplex require action frames at the same time, obviously something has to give .

    Chris Muriel, Manchester.
     

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