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why is it that my 103(ca) and 103(cb) go out first every time during a rain storm?

Discussion in 'DIRECTV Installation/MDU Discussion' started by DrummerBoy523, Oct 12, 2010.

  1. DrummerBoy523

    DrummerBoy523 Godfather

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    Jan 9, 2007
    Franklin, TN
    Can anyone offer a clue as to why I lose the 103(ca) & 103(cb) every time it rains? The signal strengths are all in the 80s & 90s on a "normal" day, but when it rains we lose those two sats first every time. My 101 numbers are in the 60s & 70s during a rain storm normally. The wife is getting fed up with how quickly our new SWMLNB system loses signal (when I thought the SWMLNB was supposed to hold on to the signal longer?).

    I have the PP but with my signals all in the high 80s and high 90s on all the sats during a normal day, I don't think I will be able to get DTV out here. I'd like to dither (whatever that is) but don't quite understand it and my dish is up on my 2nd story roof, so the access isn't good for me.

    Thoughts, suggestions, help appreciated.
     
  2. TBlazer07

    TBlazer07 Grumpy Grampy

    4,785
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    Feb 5, 2009
    You have to be over 21 to dither. :lol: Seriously though, my sigs are all mostly 95-100 for all sats and the same thing happens to me with (not that) heavy rain. That's why I won't part with my HR20's, at least I get local HD during heavy storms using OTA. Last night when the weather warnings started rolling in I moved everything to the "dash" channels. I also figure, there's always usenet so even OTA isn't that important.

    Oh, to answer your question, I believe it has to do with the higher frequency used on 103 and how the rain "absorbs" them.
     
  3. RobertE

    RobertE New Member

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    Jun 9, 2006
    Generally speaking, weather fronts and the associated storms move from west to east. So, the storm blocks 103, then 101 lastly 99. If you had the 5lnb version, 119 would be first followed by 110,103,101 & 99.

    Additionally, the Ka band is more susceptible to rain fade as the wavelength is close in length to the size of a "normal" raindrop.

    Your alignment could be a tad bit better.
     
  4. eakes

    eakes Godfather

    350
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    Sep 21, 2007
    The 101 satellite works at (nominally) 12.5 ghz, the 99 and 103 satellites work at 18.5 ghz. The higher one goes in frequency the greater the effect of rain fade (water droplets in the air), therefore 99 and 103 will fade quicker than 101 - that's pure physics, nothing can be done to prevent that.
     
  5. Manctech

    Manctech Icon

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    Jul 5, 2010
    If the LNB is going bad, despite what numbers you get on the signal meter, it will drop out faster during rain fade. Just a note.

    edit: ALSO, 103b/c are High def birds. They are much higher frequencies. The general rule is, the higher the frequency the greater the loss.

    You can always set the receiver to show the standard definition stations during rain storm.

    Hit menu - parental favs setup - system setup - display - options - show all channels.

    HD will always go out faster than SD
     
  6. Kansas Zephyr

    Kansas Zephyr Hall Of Fame

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    Jun 29, 2007
    HD/SD makes no difference.

    It's solely Ka (26.5 to 40 GHz) versus the (Ku 12 to 18 GHz) band.

    The Ka band is more attenuated by water, in any state, than Ku.

    If SD was down-linked on Ka...it would "go out" before a HD channel on Ku. D* didn't have any more Ku frequencies available...so the newest transponders are Ka. Again, it isn't an HD or SD issue.
     
  7. bobnielsen

    bobnielsen Éminence grise

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    Jun 29, 2006
    Bainbridge...
    While the Ka and Ku notations you mention are historically correct (going back to WWII and based on standard waveguide sizes), the HD satellites are in the 18-20 GHz region (18-26.5 GHz historically was called K band). Apparently there is a new notation used by Directv which refers to this frequency range as Ka. Some of the SD frequencies are actually in X band, rather than Ku.
     
  8. Kansas Zephyr

    Kansas Zephyr Hall Of Fame

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    Jun 29, 2007
    Thanks for catching my mental flip-flop...BTW. I corrected that.

    X band has even less water attenuation than Ka.

    S band less than C band, etc.

    But, again there are no "SD frequencies". It matters not what resolution, nor compression method, is being broadcast on any given channel.

    One day, if/when D* has all MPEG4 capable IRDs in the field. All of their Ku transponders (and X band) can carry all HD channels. With the IRD down-converting to SD, for SD only subscribers.
     
  9. bobnielsen

    bobnielsen Éminence grise

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    Jun 29, 2006
    Bainbridge...
    I should have stated "transponders carrying SD channels".

    I have been expecting to see Directv stop supplying MPEG2/Ku-only receivers for some time now (as announced in 2008), but it isn't happening. I suspect that the price of HD receivers hasn't dropped enough yet, but that should be the first sign of things to come.
     
  10. jdspencer

    jdspencer Hall Of Fame

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    Nov 7, 2003
    The first thing the OP needs to do is have the dish realigned to the highest possible signals on 103. My 103ca strengths are all 95+ and 103cb range from 85 to 96.
     
  11. Kansas Zephyr

    Kansas Zephyr Hall Of Fame

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    Jun 29, 2007
    +1
    Think of all the "new" bandwidth available, when D* can use only MPEG4 for delivery of both SD and HD. :)
     

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