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Rain Fade Explanation

Discussion in 'General DISH™ Discussion' started by RG6-Q, Aug 11, 2013.

  1. RG6-Q

    RG6-Q New Member

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    Apr 21, 2013
    PUERTO RICO
    I have heard you guys talk about 8psk/3/4-7/8 and maybe that is the answer to my question.

    Why is it that when it rains or is cloudy some TP go down maybe 10 points while others maybe loose 2 points???? :bang
     
  2. RG6-Q

    RG6-Q New Member

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    Apr 21, 2013
    PUERTO RICO
    Thanks for the answer. :nono2:
     
  3. P Smith

    P Smith Mr. FixAnything

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    you know ... the answer would be require extensive and long research .. some ppl get PhD for find it
     
  4. cj9788

    cj9788 Hall Of Fame

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    I am by far no expert but I can tell you that back in the day I had a one meter dish that I used on the 119 satellite and it had no rainfade issues at all while the small dish I had pointed at 110 would lose the signal completly. The rain and the clouds keep the signal from hitting the dish which causes the signal loss. Some TP's such as CONUS TP's have a stronger signal than a TP for a spotbeam. If I am wrong someone will come along and point it out I am sure. Also if your dish is not allinged correctly that may cause the signal troubles you desribed.
     
  5. P Smith

    P Smith Mr. FixAnything

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    usually SB tpns are more powerful
     
  6. sregener

    sregener Godfather

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    What causes rain fade is that water blocks the frequencies that the satellite uses to communicate with the ground. However, it does not affect all frequencies equally, nor are all the transponders delivering the same power. There is also the problem of observation - I don't believe any Dish receiver can report the strength of all TPs on a satellite simultaneously, but can only test one at a time. Thus, due to the variable nature of rain (it rarely falls at precisely the same rate for an extended period of time) that also has some impact.

    Using more power helps some to mitigate rain fade. A larger dish helps some. But no dish can overcome it all, as a heavy enough rain will block all of the signal, even with a 2-meter dish. That's just the reality of Ku-band.
     
  7. neilo

    neilo AllStar

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    I was wondering whether any of the newer DVRs have event/timer control recovery against this issue. Last night we had a heavy rain during the 9 PM to 10 PM hour which caused a signal loss and so any event scheduled during that time would lose part or all of the recording. Do newer DVRs recognize this and then record the next showing of this timer or do you still need to manually do that yourself?
     
  8. Rafael

    Rafael Mentor

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    Jul 24, 2005
    Fort...
    I totally agree, and just to add:

    Rain Fade is an absorption o dissipation of a microwave (RF) caused by atmospheric rain and mainly in the wavelength of frequencies over 11 GHz (Ku, K, Ka, etc.)
    This is why cable operators and satellite providers use their main feed out of C-Band (3 - 4 GHz). Here (over 11 GHz) the water drops or water vapor (clouds), based upon density
    send the signals to different areas than intended or dispersed causing a signal attenuation, in other words it doesn't need to be raining to suffer rain fade, a very dense cloud could
    cause the effect.

    As you may suppose low angle targets (satellites) could be affected more because precipitation could be present many miles away.

    There are some other factors that could cause those 2 - 3 points to fluctuate, temperature in the atmosphere is other factor but only noticed very slightly.

    Regarding CONUS Beam, normally satellite operators beam more power to the east coast which is said suffers more rain.
    When a satellite beams 16 Transponders (odd or even) most likely they beam 8 tps in double power and 8 in single power to extend the birds lifespan.
    So you might notice this when in rain fade effect.....
     
    1 person likes this.
  9. RG6-Q

    RG6-Q New Member

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    Apr 21, 2013
    PUERTO RICO

    Your answer to low elevation which mine is 27 suffers the most, 110 at 36 suffers second and 61.5 with 68 is the powerhouse of signal. To have signal lost on that one (61.5) either someone stole your dish or you have a CAT 5 hurricane taking place.

    I have with your info come to the conclusion that elevation is paramount in signal strength. Thanks to all.
     
  10. Jim5506

    Jim5506 Hall Of Fame

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    Low elevation in clear weather should not be a major factor. As long as you are in the footprint the signal should be strong.

    From your signal strengths it looks like your dish is misaligned.
     
  11. RBA

    RBA Active Member

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    Spotbeams are stronger if you are centered in the beam as you move further from the center the power drops off more rapidly.
     
  12. P Smith

    P Smith Mr. FixAnything

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    Only if you're out of DESIGNED area !
     
  13. cj9788

    cj9788 Hall Of Fame

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    I supose that means there are no longer any fringe areas within a DMA's spotbeam. I know that was an issue several years ago.......
     
  14. James Long

    James Long Ready for Uplink! Staff Member Super Moderator DBSTalk Club

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    The newer satellites have better designed spotbeams than the originals.

    The original spot beams were mostly circles with a focus point. Some markets were completely covered by their spots, some markets were on the fringe of the beam. Some of the larger markets did not have a spot available that effectively covered the entire market.

    Modern spotbeams are not all simple circles. They are shaped areas ... and with dozens per satellite and multiple satellites it is easier to find the right beam to cover an entire market effectively.


    As far as the fade question ... pick a a good weather day, aim the satellite dish as accurately as possible to give the best signal across ALL transponders on each satellite. With a multi orbital location dish you will need to compromise and sacrifice a high signal on one location to get a better signal on the next slot. Then when all is the best it can be write down your numbers.

    On your rain fade days look to see which transponders you are losing the most on. Losing "10 points" on a transponder/spot that is your best signal is not going to be as critical as losing "4 points" on your weakest transponder ... as long as your worst signal is still good enough to receive the points don't matter.

    One thing I noticed on my multi orbit receive dish is that I was losing more signal on 61.5 (where my spotbeam locals are) during heavy storms than on 72.7 (where ConUS Eastern Arc HD is). After the storms cleared I took a look and found that a tree I had trimmed back a couple of years ago was encroaching on the 61.5 line of sight. Wet leaves made it even more of a problem. It got trimmed and the fade is gone again.
     
    1 person likes this.
  15. cypherx

    cypherx Hall Of Fame

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    I think t would be cool if the receiver detected rain fade, it would just display the stream via your broadband connection (if available). I'm just not sure how the system could tell the difference between rain fade or other obstructions. Perhaps some kind of beacon signal sent at different bands. By measuring the signal characteristics of it, along with local radar maps (you know it can get that data via TV apps), it could tell that it's rain fade.

    You have pretty many channels available on the ipad / iPhone, and the quality is HD... It's all on the same network at home so I say let the receiver point itself to these same feeds as well. Heck maybe a two tuner DVR with both tuners occupied could watch a 3rd program via the live streaming broadband connection.


    Sent from my iPad using DBSTalk mobile app
     
  16. P Smith

    P Smith Mr. FixAnything

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    If you will take a look into DVB-S2 standard you'll find a provision (to change many parameters of a modulation, error correction, frame size, etc) to adapt to any influence between sat and user's STB;
    it has own price thought - a constant feedback, so Internet connection would fulfill the requirement
     
  17. Rafael

    Rafael Mentor

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    Jul 24, 2005
    Fort...
    RG6-Q,

    Your conclusion applies only when you consider Rain fade factor, otherwise, there are several other factors.

    Under ideal conditions in the reception area: located in conUS footprint, perfect alignment, ideal antenna size-gain, non cable loss (cable run within the range it's designed for not causing noticeable loss), good weather conditions, etc, etc. The signal strength displayed on your receiver's meter (not so accurate as a spectrum analyzer) depends on built in electronics in the ird and the lnbf; that said each receiver or lnbf has different responses even though the manufacturer claim they are the same, but each electronic component isn't exactly the same but very close. Also the software is manipulated to give more stability, parameter such as FEC could be adjusted to allow more stable signal before pixelating or loosing lock on the signal.

    For example I can open a 50 lnbf box and try them all with the same ird and antenna, some will give tremendous readings in average, others will respond better in higher odd and lower even, etc, etc...no electronic component in the world will have an exact match but there should operate in an acceptable range.

    Also antenna gain is other factor, as you increase the antenna gain aiming needs to be very accurate because it also has narrower beamwidth. Believe it or not when in Fringe you can even notice the different footprint of the bird based upon the satellite's manufacturer (US satellite operators mainly uses SSL or Boeing) but fortunately you're not so deep in fringe!!!!!

    There are more factors, but I hope you get the picture.
     
    1 person likes this.
  18. RG6-Q

    RG6-Q New Member

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    Apr 21, 2013
    PUERTO RICO
    These are not my signal levels, they are elevation. I get on a clear day on 119 TP1 SPOT is 88, TP 3 SPOT is 94, TP 16 Non-Spot is 80 and so forth. It just seems to me that elevation at 27 with signal of say 80 is less than 80 on a 45 degree angle dish. Clouds seem to always accumulate low in the horizon. Does the signal have to travel through more rough weather at low elevation than higher ones.????
     
  19. Jim5506

    Jim5506 Hall Of Fame

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    Depends on the weather.

    If you have a storm between your dish and the satellite, there will probably be more water vapor between the dish and the satellite, therefore more signal scattering/attenuation, but with clear skys little difference will be noted.

    Normal cumulus clouds will not do too much damage to the signal, they are just visable water vapor whereas a storm can include ice being thrown up into the cloud tops (hail) and rain plummeting downward.

    Rain drops are a much higher concentration of water molecules than clouds.
     
  20. Rafael

    Rafael Mentor

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    Jul 24, 2005
    Fort...
    I believe the answer to this is your location (Puerto Rico) assuming your dish is perfectly aligned.
    The spot beams you have with higher levels means that indeed they're covering well the island......
    But the conUS beam isn't 100% beamed to your area, their main target is with continental 48 states, and then shared with your area (USVI & PR), they aim in such a way that the spill over feeds your area with good enough power to have a respectable level of 80.

    What size antenna do you have?

    Here's a link so you can see the conUS beam shape:

    http://www.satbeams.com/!ajax/embed?beam=6269
     

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