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Thread: LNB to Dish spacing.

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    Default LNB to Dish spacing.

    Some time back I asked about using an IPSTAR Internet dish for other uses.
    That dish I was eyeing off didnt become available but yesterday I was offered another one including the Modem that has been dismounted from a house.
    I was surprised at just how big the LNB in on this dish and the distance from the Dish surface.
    The LNB is on an Offset braced arm wheresas mine is a self supporting offset arm.
    The Mast is big too, about 3&1/2 in diameter.
    This dish is Firbeglass, 1.37m (54 inch) high X 1.23m (48 inch)wide'
    The front of the LNB is 1 metre from the dish surface.
    The LNB is 480 mm (19 inches) overall and it has TWO 'F' connectors on the top end (Tx) with one capped off.
    Why the 2 'F' connectors on the Tx of the LNB ?
    The Rx lnb is at the front just behind the horn and has its own 'F' connector.

    I didnt think this dish was that overly big so why set the LNB so far out, even supported as it is?
    Last edited by gordon_s1942; 16-02-10 at 05:01 PM.



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    One F connector is to receive signal,
    The other F connector to send data-(modem)..

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    Talking Basics of the Parabolic Reflector.

    Quote Originally Posted by gordon_s1942 View Post
    Some time back I asked about using an IPSTAR Internet dish for other uses.
    That dish I was eyeing off didnt become available but yesterday I was offered another one including the Modem that has been dismounted from a house.
    I was surprised at just how big the LNB in on this dish and the distance from the Dish surface.
    The LNB is on an Offset braced arm wheresas mine is a self supporting offset arm.
    The Mast is big too, about 3&1/2 in diameter.
    This dish is Firbeglass, 1.37m (54 inch) high X 1.23m (48 inch)wide'
    The front of the LNB is 1 metre from the dish surface.
    The LNB is 480 mm (19 inches) overall and it has TWO 'F' connectors on the top end (Tx) with one capped off.
    Why the 2 'F' connectors on the Tx of the LNB ?
    The Rx lnb is at the front just behind the horn and has its own 'F' connector.

    I didnt think this dish was that overly big so why set the LNB so far out, even supported as it is?
    G'Day Cobber,
    As simply as I can put it, the focal point is a function of the shape and depth of the parabolic reflector and not so much the size.
    By the way, it would have a mesh embedded in the fibre glass.
    I think this link will give you a grounding in the principles involved.



    Have fun,
    Kindest Regards, " The Druid ".


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    conaxle, you didnt read my post correctly.
    The LNB has THREE 'F' connectors, TWO on the back of the Tx LNB with ONE capped off.
    The Rx LNB is mounted just behind the feedhorn and has its own 'F' connector.
    The cables are still attatched to the LNB as they were when it was in use.

    Beer4life, my maths are shit, plain and simple, I dont know Convex from Convoy but I do understand that the Dish is shaped to reflect the incomming satelitte signal to a 'Focal Point' ie the LNB feed point.
    Its just this dish is so different to mine with this seemingly massive supported LNB arm when my IPSTAR dish doesnt.
    I was thinking along the lines of cost and stability of the LNB perched out there.
    I only mentioned it was Fibreglass because mine is pressed tin.
    I do have a Prodeline 1.8m Fibreglass offset dish sitting doing nothing and I know its got a mesh imbedded for both Ku and C band.
    Fibreglass I understand has very poor electical conductiverty and makes a lousy reflector of Radio waves without either an imbedded mesh or metallic surface.

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    Gordon, I forgot to mention the 3rd F connector that is capped is a spare one,for if you want to use it for different applications like Voip,Multicast,Video Conferencing etc.
    We use these for training porposes in our dealers at work..

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