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Rain fade - HD only

Discussion in 'DIRECTV HD DVR/Receiver Discussion' started by lparsons21, Sep 26, 2011.

  1. lparsons21

    lparsons21 Hall Of Fame

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    Mar 4, 2006
    Herrin, IL
    Yesterday we had about 3" of rain fall over the day and I had rain fade most of the time on my HD channels with the exception of my locals in HD. Here are my signals :

    101
    96 95 96 87 95 97 95 97
    96 96 96 0 96 98 95 98
    95 0 96 96 96 99 96 98
    95 77 95 0 96 98 95 100

    #110
    8=96 10=97 12=95
    all the rest N/A

    #119 - all mid to high 90's

    #99(c)
    87 93 88 93 88 89 88 92
    86 91 88 92 89 94 all the rest N/A

    #99(s)
    85 85 93 89 90 86 NA NA
    NA NA NA NA NA NA 64 0
    84 85 0 0 0 0 63 34
    rest NA

    #103(s)
    0 0 44 0 0 0 NA NA
    NA NA NA NA NA NA 92 88
    73 68 86 90 64 73 95 95
    rest NA

    #103(ca)
    88 89 91 91 89 88 90 92
    88 91 91 91 88 90 92 93
    rest NA

    #103(cb)
    88 93 86 91 83 89 86 91
    86 89 85 90 85 91 NA NA
    Rest NA

    SWM
    100 98 97 0 0 0 0 99
    95 rest NA

    Does this indicate some problem that I need to address? I noticed a few very low numbers, but not all on one bird.
     
  2. bpratt

    bpratt Godfather

    647
    6
    Nov 24, 2005
    Salt Lake...
    The low numbers you see are probably spot beams that you are close to. I purchased a device which allows me to adjust my own dish. The numbers you are seeing look great to me and I don't think they could be improved upon. Your HD channels come from the 99 or 103 dish. They won't be as high as the 101, 110 or 119 dish because the HD broadcasts uses a narrower beam.

    I think you will have to live with rain fade when you get that much rain in one day.
     
  3. veryoldschool

    veryoldschool Lifetime Achiever DBSTalk Club

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    It's hard to say, since the numbers you posted are bit error rates and not signal power levels.
    HD [Ka] uses higher frequencies [not narrower beams], which are affected by rain more.
    Your local HD channels do come from a "narrower" [spot] beam, which has a higher power density, which is why they fade last.
     
  4. lparsons21

    lparsons21 Hall Of Fame

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    Herrin, IL
    Thanks for the feedback. Basically you are both saying things are what they are. I can live with that because normally rains are not that heavy for that long around here.

    VOS, I thought what I was posting was signal strengths, that is what D* calls them on their menu selection...
     
  5. veryoldschool

    veryoldschool Lifetime Achiever DBSTalk Club

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    They are all you can get out of the receivers.
    They are more a "reflection" of signal strengths, which is more a quality of the signal than the strength.
    A good quality signal [carrier to noise ratio, aka CNR] reports good numbers.
    If power was being measured, you'd see different numbers between short coax runs and long coax runs.

    Now since you're using a SWiM, things [power wise] get even harder to measure, since the SWiM has an AGC [automatic gain control] that keeps its output constant [within its range], until it can't anymore.
    You "might" reduce some of the fade by using coax/splitters with the least loss that you need, as the whole system has to work as one, and losses from the SAT [rainfade loss] to the receiver [cable/splitter losses] all add up.
     
  6. lparsons21

    lparsons21 Hall Of Fame

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    Herrin, IL
    Thanks.

    The current wiring is SWM LNB to 4-port splitter. One port for power inserter and then on to the CCK, one port to the upstairs HR and one port to a 2-way splitter that feeds 2 HRs.

    Longest cable run is to the upstairs, about 35'. The 2 runs into the house to the dual HRs is about 20' max.

    With the locations and the number of HRs I have, my wiring and splitter usage is as minimal as it can be.
     
  7. veryoldschool

    veryoldschool Lifetime Achiever DBSTalk Club

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    I think your setup is pretty close, "although" if I have signals upstairs and lost them on the DVRs off the 2-way, I'd try removing the 2-way and adding a coax back to use the fourth port of the 4-way. Should improve things by ≈ 5 dB.
     
  8. lparsons21

    lparsons21 Hall Of Fame

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    I thought about doing another run, but I'm too old and my son's too fat for crawling under the house. And the neighbor with the kid that could and would crawl under the house has moved away, so that might never get done. But I'll keep it in mind.

    I wonder if moving the 2-way to feed the cck and one HR would be a better connect than the way I have it now? Distance is the same though as the CCK is in my man cave.
     
  9. TBoneit

    TBoneit Hall Of Fame

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    You have now hit one big difference between DirecTV and Dishnetwork.

    All of DirecTV HD AFAIK comes from satellites that suffer more rain fade than the type of satellite Dishnetwork uses.

    I do remember that My parents Dishnetwork system pretty much kept all the channels throughout Irene and Lee with a few momentary interruptions. She is on the Eastern Arc.

    I had the HDTV in her TV room going keeping an ear on the weather as I was using the wet/dry vacuum to suck up the water that all that rain had leaked into her basement for a good part of the night. My brother came down to help as I was running out of steam from it.

    Side note: First time I ever saw her get water into that part of the basement. So much rain. We still do not know where it came in from. First Theory was redirect the drain spouts further away from the house, Second theory was put plastic over the window well. Still got water. My suspicion was that the ground was so saturated it found a way in. the parents have had that house since the 60s. First time for water in that part of the basement. Once in the past on the other side when it was raining heavy every two days, even then only a little amount. Overall a good dry basement.
     
  10. TBoneit

    TBoneit Hall Of Fame

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    If it is in a crawl space I'd be worrying about moisture affecting it.
     
  11. JonW

    JonW Icon

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    Rain fade and snow fade are a consistent draw back with DirecTv. Most storms shouldn't cause a problem, but the really dense ones will.

    If you start losing signal in high winds, however, your dish may be coming loose from your roof.

    DirecTv used to (and hopefully still does) monitors outages and must compare them to others in your area. They actually contacted me about my signal problems, and ended up pretty much re-installing the dish, cables, switch, etc.
     
  12. lparsons21

    lparsons21 Hall Of Fame

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    I pretty much knew that and had forgotten that was an issue from last time I had D*. I was remembering that my EA Dish setup didn't suffer much from rain fade at all. Took one heck of a storm to make it go out. Yesterday's would have for part of the time, but not quite as long as it took out my HD on my D* setup.

    Not a huge deal as I always have tons to watch from recordings and my internet is there for VOD or live streaming.

    Fortunately for me, during the time rain fade was an issue, I was watching recordings of earlier things (Solheim Cup). My son was grousing a bit as the early football games were being clobbered. I'm glad it all cleared up before his sainted Chargers were on, I'd still be hearing him bitch today if that had happened!! :lol:
     
  13. veryoldschool

    veryoldschool Lifetime Achiever DBSTalk Club

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    You'd be trading off the loss to 2 DVRs verses to the one, which might be worth it :shrug:
     
  14. lparsons21

    lparsons21 Hall Of Fame

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    Only complete wiring is in the crawl space. No connectors, splitters, etc involved down there.
     
  15. veryoldschool

    veryoldschool Lifetime Achiever DBSTalk Club

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    Dish is still using the Ku SATs, while DirecTV is using the Ka [higher frequencies] for HD and Ku for SD.
     
  16. TomCat

    TomCat Broadcast Engineer

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    If you have a local spot beam, those numbers are a bit low. You should easily be able to get 96-100 on at least one transponder on 99 or 103 (96 at the edge of the spot beam, 100 at the center or within 35 miles of the center). If you can't, that implies misalignment. You are close, at 95, but the right combination of rain or rain clouds will still be an issue even if you have perfect reception.

    Spot beams are not smaller for Ka; it is easy to engineer the desired footprint to whatever size they want regardless of whether Ku or Ka. Spot beams on the east coast where markets are densely packed may be 250 miles across while those in the western states which are far apart can be 400 miles or more in diameter. Only on the edge will rain fade become a real problem assuming good alignment, but enough rain will wipe any signal out on any antenna anywhere.

    A misaligned dish will lose HD before SD because the Ka focal points are smaller, not because the signal is weaker or that much more susceptible to rain fade. IOW, you can be off a bit in alignment and SD channels will not have dropped as much, and then when the rain comes the rain fade margin being lower for those channels means you will lose them easier.

    On the other hand, the larger reflector on the KaKu dish is larger for a reason, which is so that the rain fade margin of a properly aligned KaKu dish matches more closely for Ka the rain fade margin of a properly aligned older dish for Ku. But this also increases the RFM for SD or Ku channels even more, so it is not that there is less RFM of HD compared to what we have come to expect for SD on older dishes; that is about the same. But it is indeed lower compared to SD on the same new dish, just not all that significantly lower.

    The concept of Ku being hotter than Ka is a myth; the antenna system is designed to match the levels of Ku to Ka at the output of the various LNBs, or to engineer Ku to be even be slightly lower than Ka to compensate for the uneven cable loss post-antenna. The general idea is to engineer the system so that both Ka and Ku signals reach the front end of the receiver at the same levels. If that was not done, one signal might overload the AFC and swamp the receiver creating reception problems for the others, as all signals must be ideally in center of the operational window of the IF section. Whether they reach the dish at higher or lower levels is irrelevant because that difference is engineered out so that the levels will be the same at the receiver.

    This myth is further complicated by how large the rain drops and water molecules in clouds are. If they are nearer to the size of the wavelength of Ka, they will act like little absorbers and absorb or attenuate the signal level as measured at the feedhorn rather than simply refracting it (which does not really reduce the signal level). Consequently if the rain drops are closer in size to the wavelength of Ku, those channels will become attenuated more instead.

    So, bottom line, the better your dish is aligned the more RFM you have, and misalignment affects HD more than SD. But on a perfectly aligned dish, while you will have a little more RFM for SD than HD, depending upon the particular weather event, you could lose SD first, although somewhat less likely than losing HD first because it is more likely that raindrop size more-closely matches Ka than Ku.

    If you lose HD first about 65% of the time and SD first about 35% of the time, that indicates the probability of a good alignment. If you lose HD first and often, and rarely if ever lose SD first, that raises the possibility of a not-so-good alignment.

    The best defense is a perfect alignment, especially in a rainy environment. Since many installers still align only for Ku (because Ka meters are expensive), a proper dithering technique is about the only way to ensure perfect alignment.
     
  17. JonW

    JonW Icon

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    Satellite's also move around. Their position can be corrected from the ground, but drift is normal. It's kind of hard for the average home owner to maintain perfect reception unless they learn how to climb up on their roof and check the alignment of their dish.
     
  18. veryoldschool

    veryoldschool Lifetime Achiever DBSTalk Club

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    :confused:
    I'm not quite sure what to say.
    While drift is normal, the amount before it is corrected is so minor as to have no effect on the customer's dish alignment.
     
  19. MysteryMan

    MysteryMan DIRECTV A-Team DBSTalk Club

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    +1......I think it's safe to say that those who design these satellites took drift into consideration and allowed for it to have minimal impact.
     
  20. veryoldschool

    veryoldschool Lifetime Achiever DBSTalk Club

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    "Safe"?
    Well I'd say the SATs would be playing "bumper cars" with the others at the same orbital slot long before the customer's dish would show any signal change. ;)
     

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