LNB distance to the Dish

Discussion in 'Fringe Reception General' started by petert74, Sep 30, 2008.

  1. petert74

    petert74 Regular Member

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    My Satellite Setup:
    1.3m dish
    Panasonic Digibox
    My Location:
    Spain
    Can anyone tell me for those who live in Southern Spain, were the LNB should be positioned.

    Not the rotation but whether it should be as close to the dish as possible or as far as possible.

    Obviously this will impact on the signals being bounced off the dish so I would be grateful if I could get an answer.

    Many thanks

    p
     
  2. satelliteman

    satelliteman Administrator Staff Member

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    The focal length can be set with the use of a satellite meter and adjusting for maximum signal.

    Are you using an LNBf or c120 with adjustable feedhorn?
     
  3. hoppo1

    hoppo1 Guest

    730mm for 1.9 or 930mm for the 2.4 for the Portuegues dishes. 800mm for the Tecatel dish.
     
  4. Channel Hopper

    Channel Hopper Suffering fools just so you don't have to Staff Member

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    _http://www.analyzemath.com/parabola/parabola_focus.html
     
  5. Satcom1

    Satcom1 Regular Member

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    My Satellite Setup:
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    Diamond 9000 HD, 1m prime focus, 1.2 m prime focus, both on C Band.
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    No matter where you are in the world the dish will have the same f/d.

    The Skew changes with where you are and what satellite you are aiming at.

    The simple way to peak your LNBF is to watch your receiver's signal display and adjust f/d and skew for maximum Signal Quality not strength.

    Here is how you find your dishes f/d.
     
  6. aba

    aba Regular Member

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    My Satellite Setup:
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    ehcostar ad3600ipvia
    3 dishes zone 2 / 1 mt motorized / 2.3 m motorized
    My Location:
    nottingham
    What dish have you got off set or prime focus and what size dish
     
  7. petert74

    petert74 Regular Member

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    My Satellite Setup:
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    Panasonic Digibox
    My Location:
    Spain
    Thanks againg to all. To be honest its all getting a bit technical for a non qualified hobbist. I was only really looking for a simple "close to the dish" or as far from the dish as possible. but i guess its not that simple.

    Thanks everyone.

    pt
     
  8. Channel Hopper

    Channel Hopper Suffering fools just so you don't have to Staff Member

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    It would be a lot easier if you gave answers to the earlier questions
    (dish manufacturer, size and/or type). Even a photo would be a start to nailing down a benchmark figure to begin with.
     
  9. petert74

    petert74 Regular Member

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    My Satellite Setup:
    1.3m dish
    Panasonic Digibox
    My Location:
    Spain
    Many many thanks for your continued support.

    My lnb is very new, its a Smart Titanium TWIN 0.2db LNB Universal. The receiver is a Pace 460 (i think, its the white low frequency one for frinde areas.

    Cable, I have no Idea, its a standard cable I got from a DIY megastore here near GIB.

    I heard the Smart should be a good quad, but every one here seem to be using the Televes single 0.5db (orange in colour).

    Has anyone every had any experience with the smart twin. Ive replace the Televes because I wanted to run a second cable into another room.

    No soap in the evening so the OH is not happy!!!!

    any advice???

    thanks in advance
     
  10. Channel Hopper

    Channel Hopper Suffering fools just so you don't have to Staff Member

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    So is it a quad or a twin ?
    Some earlier posts on the forum were very impressed with other quad LNBs over singles or twins , possibly owing to the better switch matrix within them, but others are adamant that a single with the right feed and transfer ports will always be a better match to the dish.

    I would go for a single as these can be matched to a dedicated feed, but then if you have the resources then I would try both and report back with the results.

    As for the soap - that is surely a cause for celebration.
     
  11. petert74

    petert74 Regular Member

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    My Satellite Setup:
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    Panasonic Digibox
    My Location:
    Spain
    Hi its the twin I have, the issue is that its perfect all day, but come 8pm local time its start to break up and by 9pm ITV and BBC channels are unwatchable.

    The reason I wanted a twin/quad is to run at least one other feed into the house so that I can escape the soap and the kids channels.

    Last night I put back the televes single (orange) that seems to be used everywhere here in Southern Spain. Its only a 0.5db and one of the cheapest LNB about, but it works better than any other single, twin or quad I have every tried and believe me I have tried a few!!!

    Has anyone used a Televes Twin or quad, I dont know why the Televes single is so good but they seem to know what they are doing, so I will now ask at my local retailer and they will promise to have it in a few days but I know it will take about 6 weeks like the twin that was no good.

    Televes twin anyone????
     
  12. snapper23

    snapper23 Member

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    My Satellite Setup:
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    Hi
    Fitting a zone2 dish with twin lnb - read the thread - did the parabola equation exercise and f (focal distance) came out at 396 mm = What a pity my feedarm is only 350mm long.

    f = D squared divided by 16c - I DONT THINK SO !!!
     
  13. guest poster

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    That calculation is for Prime Focus dishes which are easy...... it's a bit different on standard offset dishes.... and very different on a $ky dish....

    How did you measure D... horizontally ... Vertically... Diagonally (or c for that matter) ? The F/D Ratio on a $ky LNB is different H & V and it's offset inside the feed horn to allow the dish to appear horizontal at 28e
     
  14. aba

    aba Regular Member

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    My Satellite Setup:
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    ehcostar ad3600ipvia
    3 dishes zone 2 / 1 mt motorized / 2.3 m motorized
    My Location:
    nottingham
    but can you please tell us what dish you are useing
    you have told us about lnb coax receiver everything but the dish
    and if its the focul point you are after it the dish that we need to know

    and to people who are still trying to help you this thread is now 3 months old
     
  15. guest poster

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    In practice, if you do try to calculate the focal length and F/D ratio on a standard offset dish (not a $ky dish), the calculation for the focal length can work in the vertical*, the horizontal* or diagonally*. It depends who designed the dish and unless you have that design brief to start then to find the optimum focal length is very difficult.... if say you had to make an offset LNB arm for a dish face without an arm. Probably the most reliable way is to calculate the position/ angle of the round dish face view as would be seen by an offset LNB and then calculate the optimum focal length (on that axis).

    *That is that you measure D vertically and use a straight edge across the dish face vertically to gauge the depth d (or c in that example equation).

    The F/D ratio should work across the horizontal for the whole (normal) offset dish. On $ky dishes the F/D ratio of the feed horn reflects the shape of the dish (plus allowing for the fact that the LNB arm is in offset).

    We've modified a lot and this is sort of important to modify or check a dish if you really want the most out of it.
     
  16. snapper23

    snapper23 Member

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    My Satellite Setup:
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    pent4 winxp
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    uk
    Hi
    I am using a COMAG zone 2 offset dish 60cm to receive the new freesat system. My problem was the lnb could move for and aft 20mm (slide) . It is a dual lnb hdi ready comag lnb. The height is sucjh that i cannot reach the lnb to adjust when in position - so i needed to set up the lnb first - i can adjust azimuth and elevation from the window but not the lnb skew for or aft position . So i searched for ??lnb set up calculation and found they were no help BUT you have now explained many variants - at the moment my quality is only 65 %
     
  17. aba

    aba Regular Member

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    ehcostar ad3600ipvia
    3 dishes zone 2 / 1 mt motorized / 2.3 m motorized
    My Location:
    nottingham
    well untill petert74 tells us what dish he is useing nobody can help
     
  18. dabba1

    dabba1 Member

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    My Satellite Setup:
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    will this help ?

    _http://www.sadoun.com/Sat/Installation/LNBF-Installation.htm

    I am no expert but looking at this,which appears to be a general setting, the LNB is required to be furthest away from the dish !!
     

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