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  1. #1
    Junior Member Teacher
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    Default No Signal during rain !


    Friends

    Yesterday there was heavy rain at my place and I surprised that during rain the signal level/quality drops down from 90% to 25% and I were not able to watch the live show of Antaltics Landing
    WTF is it ? Is it a normal thing.
    I'm using 100cm offset dish+0.2 dB Ku-band LNBF and pointing to INSAT4B.

    Plz put ur comments.

    Thanx
    Technology Makes You Live

  2. #2
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    you need alot bigger than 100cm dish. in that way during heavy clouds rainy season your dish can compensate its signal reception.
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  3. #3
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    It usually happens with Ku band signals & offset dish, I have have the same problems but not on my prime focus dish with C band.
    If you notice on some roof tops some of the LNB are covered with a bucket like plastic case, not sure if this is to prevent the LNB from heat or protecting from rain.

  4. #4
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    Quote Originally Posted by urpradhan View Post
    Friends

    Yesterday there was heavy rain at my place and I surprised that during rain the signal level/quality drops down from 90% to 25% and I were not able to watch the live show of Antaltics Landing
    WTF is it ? Is it a normal thing.
    I'm using 100cm offset dish+0.2 dB Ku-band LNBF and pointing to INSAT4B.

    Plz put ur comments.

    Thanx
    use little biger than 100 cm., i am receiving hbs even in rain time with my 12 feet dish.

  5. #5
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    C-band is unaffected by rain fade, only Ku band, the answer could be a bigger dish, But how much bigger, is a good question. We know that 2.4 meter [8 ****] dishes are unaffected by rain, unless it's monsoonal very heavy downpoor. Off-set and prime makes no differance, it's not the dish but the Ku signal
    regards from OZ bassett

  6. #6
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    ku is ok, but signal maybe weak. to compensate, get a bigger dish.
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  7. #7
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    Read More About Rain Fade

    Rain Fade




    Even the most reliable satellite communications technology can sometimes be out-matched by the forces of nature. It’s a phenomenon known as “rain fade” or “rain attenuation” – a weakening of the satellite signal as it passes through raindrops.

    Rain fade is one of the most common, and often most misunderstood, phenomena to affect satellite signals. But the more you learn about the causes of rain fade, the better your chances are to lessen its impact on your satellite system.
    The Causes

    Any satellite communications system network operator using a Ku-Band system (12/14 GHz or higher frequencies) will face the effects of rain fade at some time. But to understand why this weakening occurs with Ku-Band transmissions, you must first understand the causes of rain fade. Two of the most common causes are listed below.

    1. Absorption – Part or all of the energy generated when a radio wave strikes a rain droplet. The droplet is converted to heat energy and absorbed by the droplet.
    2. Scattering – A non-uniform transmission medium (the raindrops in the atmosphere) causes energy to be dispersed from its initial travel direction.

    Scattering can be caused by either refraction or diffraction:

    * Refraction – The refractive index of the water droplets encountered by the radio wave.
    * Diffraction – the travel direction of the radio wave also changes as it propagates around the obstacle in its path (a water droplet).

    These different reactions ultimately have the same effect – they cause any satellite system to lose some of its normal signal level. Don’t expect to lose your satellite signal every time it rains, though. Rain outage will only occur during the heaviest rains (convective and stratiform are the most predominant types) with only a small portion of the transmission path experiencing attenuation. In fact, of a typical satellite transmission path measuring 22,300 miles, less than .02% will be affected by rain fade.
    The Impact of Rain Rate

    Rain rate is the most common factor used to determine rain fade. Rain fade seems to correlate very closely with the volume of raindrops (expressed in cubic wavelengths) along the path of propagation. This is opposed to the common misconception that the degree of attenuation is proportional to the quantity or individual size of the raindrops falling near the receive site.

    Pinpointing the specific factor that lead to attenuation is essential to accurately predicting the problem. Models can be developed from this data to chart the effects of rain fade on a regional or individual site basis. From this information, you can determine the correct antenna size you’ll need to counteract the effects of rain fade.

    This doesn’t mean, however, that buying the largest antenna possible will solve all rain-related problems. There is a point (usually under extremely heavy rain conditions and only for very brief periods) where virtually 100% of the satellite signal is absorbed by rain and no increase in antenna size will raise availability.

  8. #8
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    Quote Originally Posted by urpradhan View Post
    Friends

    Yesterday there was heavy rain at my place and I surprised that during rain the signal level/quality drops down from 90% to 25% and I were not able to watch the live show of Antaltics Landing
    WTF is it ? Is it a normal thing.
    I'm using 100cm offset dish+0.2 dB Ku-band LNBF and pointing to INSAT4B.

    Plz put ur comments.

    Thanx
    During these monsoon rains even signals from bigger dishes drops to zero. In Chennai when there were heavy rains there was no signal even on a 8 feet dish. We cannot compare Ku band with C band which is not much affected.

  9. #9
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    Quote Originally Posted by dom06 View Post
    It usually happens with Ku band signals & offset dish, I have have the same problems but not on my prime focus dish with C band.
    If you notice on some roof tops some of the LNB are covered with a bucket like plastic case, not sure if this is to prevent the LNB from heat or protecting from rain.
    It is to prevent the precious lnb15ks from rain and sun In olden days we didn't have those moulded & sealed LNBFs like now. We have to assemble the lnb with feedhorn. Lnbs had screws over the top. So some times water enters through them. So we had to use weather covers to prevent water from entering into the lnb.

  10. #10
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    usually, the signal of a ku band is drop to 3dB ( half the power is loss)during heavy rains and even you got a bigger dish, you still experienced a no signal. but if this heavy rains is also happened in the uplink provider then they can compensate the signal losses by increasing the power of their H.P.A. or transmitter to a certain level. thats why, even a heavy rain is in your area then you got a good signal.

  11. #11
    Alexius
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    what you need to do is move...

    the problem is the size of the raindrops here in the tropics is perfectly suited to disrupting Ku band communications... if you move somewhere like england which has smaller rain and hence doesn't suffer rain faide on Ku as much... when I had sky digital in England, with the 60 cm minidish, it only vanished once, when it was hailing... ( falling ice)

  12. #12
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    Thumbs down

    Thank you friends for your valuable inputs.

    But I'm in a 47 EIRP region, and all the DTH players are offering even 40cm dishes for INSAT 4B/NSS6. Even though I have 100 cm dish which is enough to get best signal in my region.

    Then if its a technical drawback of Ku-Band signals then how these commercial DTH players will survive to retain their customers ? In other words we can say RAIN = NO SIGNAL = NO TV

    Again Can I put a plastic or polythene cover to my Ku-Band LNBF and will it reduce the rain effect to some extent ?
    Technology Makes You Live

  13. #13
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    i don't think it does any better improving signal quality.... lnb plastic covering is merely to protect the lnb from foreign elements such as too much exposure to sunlight (u/v rays) corrosion from exposure to rain water.
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  14. #14
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    Quote Originally Posted by urpradhan View Post
    Thank you friends for your valuable inputs.

    But I'm in a 47 EIRP region, and all the DTH players are offering even 40cm dishes for INSAT 4B/NSS6. Even though I have 100 cm dish which is enough to get best signal in my region.

    Then if its a technical drawback of Ku-Band signals then how these commercial DTH players will survive to retain their customers ? In other words we can say RAIN = NO SIGNAL = NO TV

    Again Can I put a plastic or polythene cover to my Ku-Band LNBF and will it reduce the rain effect to some extent ?
    Many providers use large dishes to uplink content 15m.

    Taiwan has heavy monsoon rains. For Dream tv which is 56dbw I use a 1.8m solid ku. Your issue is that you need a larger dish. try a 1.8m. Huge difference over a 1m.
    If Evolution works, why so many idiots?


  15. #15
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    Quote Originally Posted by norman23 View Post
    what a silly advise from an..ähhhh, engineer...

    i case of very heavy rainfall, only the pope could help!
    but i do not know, how much the vatikan is charging...
    Obviously Norman you are a fool and are not here to help anybody.

    I didnt get called best satellite installer in Taiwan in the latest Tele Satellite magazine for being a retard.

    The larger the dish the better gain in attenuation. So when you have a large amount of rainfall larger dish has more attenuation therefor the signal can stay above the minimum amount needed for reception.

    After all I only live in a country with the world records for amount of rain per hour... try over 300mm of rain per hour.

    Dish size will depend on how much eirp you have in the first place and the quality of your lnb and dish, then you factor in rain fade.

    Obviously with your pea brain you can't understand all this. lol

    But as my wife tells her friends.... bigger is better and I'm a man who knows how to use his large tools.
    If Evolution works, why so many idiots?


 

 

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