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Thread: Cascading Multiple Dream Boxes

  1. #1
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    Default Cascading Multiple Dream Boxes

    My mate tells me he has connected multiple dreamboxes with a single dish and LNB feed. i.e. the antenna out on the first Dream is fed into the second dream and so on.

    Now I thought that there is a problem with this, the key issue being the satellite Horizontal and vertical signals.

    I have asked him to have one box tuned to a Horizontal channel eg TV1 and the other box set to a vertical channel eg CNBC and he says it works fine.

    Can other members here kindly please advise and or supply their experience with this kind of setup...... Thanks



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    You gotta see it to believe it.

    I'd go with your previous thoughts being correct.

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    2 words checkitout

    NO HOPE

    As long as all the units are on either H or V then yes they would be ok but the minute the first unit in the chain was on TV1 and any other unit tried FBO they would have a blank screen due to the fact that the first unit in the chain is sending the voltage to the lnb has triggered the H and that is what will be coming into it and all others

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    Senior Member Dave001's Avatar
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    I've never done it myself, but I've read it can be done.

    You set the LNB skew out by 45 degrees. You loose a lot of signal, but it allows you to receive both polarities at the same time.

    Dave

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    i hear that for $50 a multiswitch will solve the issue at hand.

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    Hi You Need a twin Lnbf


    Like that
    and also you need

    two input multi switch like this


    Thanks
    Rarg

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    Quote Originally Posted by checkitout View Post
    I have asked him to have one box tuned to a Horizontal channel eg TV1 and the other box set to a vertical channel eg CNBC and he says it works fine.
    Not possible. The STB outputs 18V to set the LNB to output the horizontal polarity, and 13V to set the LNB to output the vertical polarity. If one STB was outputing 18V (because it was tuned to a channel on the horizontal transponder) and the other was outputing 13V (to get the vertical) then the higher 18V signal would override the potential of the 13V output. The LNB would have 18V DC across its output and be set to horizontal only.

    It's physically impossible to have both polarities being sent down the same cable at the same time since they are sent at virtually the same frequency from the sat (only a 9MHz offset between the centre frequency of each horizontal and vertical transponder which is a quarter of the 36MHz bandwidth of each transponder).

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    Quote Originally Posted by Dave001 View Post
    You set the LNB skew out by 45 degrees. You loose a lot of signal, but it allows you to receive both polarities at the same time.
    Yeah, you would receive both at the same time but the signal couldn't be decoded since the two signals are occupying the same frequency. Only if one signal was significantly more powerful than the other could anything be decoded and you could only then receive the more powerful signal.

    There is a very good reason why the bandwidth is split between horizontal and vertical polarity and that is to provide twice the capacity for the same frequency spectrum, but it's only achievable with accurate antenna orientation and correct switching between them. If the orientation isn't correct then you'll get interference that will substantially increase the BER.

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    I am using Above setup for many years without any problem
    Thanks
    Rarg

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    Senior Member nfnovice's Avatar
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    which set-up are you using rajan ?
    twin lnb to multiswitch - that will work every time
    cascading in/out dream to dream on single lnb - that will fail every time you are on different polarities

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    Hai
    I mean twin lnbf With Multi Switch
    Thanks

  • #12
    Junior Member tican2's Avatar
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    I have just changed my LNB from single to dual outputs for that reason.

    Tican2

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