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Thread: prime focus dish

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    Default prime focus dish

    I have a prime focus dish and wish to change lnb to 10700 but they all appear to be only suitable to use with an offset dish. Why can't you use this type of lnb on prime focus dish. My original lnb is a caltek 11300 model

    Hope someone can explain to me



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    Offset lnb only suitable for that type dish. An offset dish is really, in simple terms, only part/segment/portion of that total dish you have. The lnb only "sees" that smaller reduced area, and sees the rest as "noise".

    Your prime parabola is designed for the whole dish you have, focussing the whole dish area into your prime feed.

    You need to buy a prime feed, possibly even a combined C and KU band LNBF all in one, may be better for you, so you can use your dish for both bands.

    Hope this helps......

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    Default

    I have used offset ku lnb's on c band prime focus dishes in the past.

    As viewer mentioned a offset dish is a section of a prime focus dish.

    What i use to do is bolt offset ku LNB's onto the side of a prime focus Cband LNB.

    Then id have the capacity to use both on one dish, the KU LNB use to point into the side of the dish to catch the correct profile like a offset dish.

    But note that you would not be making full use of the dish, just a small section of it.

    In my case it was used on 2.3m mesh dishes, i only needed a small area like a traditional 60-90cm dish to get the ku channels i was after, not the whole 2.3m

    For maximum signal get a prime focus LNB and make full use of the dish, most sat shops sell them.

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    Thank you guys for the replies

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    Yes Godzilla, used to do the same as you too!

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    its not about function difference between offset and prime focus
    its more about mounting points and bolts
    mate of mine used to make a holder to hold the offset lnb in a prime focus position
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    Yep, done that too with a piece of villaboard (stuff used on wet area walls) as a holder.

    The most successful way I actually did it was to actually cut a v wedge out of the section of the cband scaler ring (didn't effect the cband signal), and fit the Ku band inside the wedge, and ever so slightly have it facing to the centre of the dish.Naturally enough, if I was on say PAS8 C transponder, I would need to give the actuator one bump to get to the Ku signal properly. Then I got an auto positioner, and that made things really easier. Worked fine for years and years...this was all 15 years ago when we had little choice in equipment...now all you need is the combined feed.

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    Default

    So, would a regular C band LNB work on an offset dish? I'm reading online that some people are getting good signals from IS5 C-Band such as Australia network and BBC with 90cm offset dishes. Just wondering if I could use a regular LNB or if I need an offset C-Band model.

    OC

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    Yes, they are getting IS5 via a regular Cband feed and offset dish

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    Default Prime focus Ku LNB (twin output)

    My prime focus KU LNB 10700 (twin output) failed and I had trouble finding a replacement. Satplus in Victoria found one for me,
    It was not in their normal line up, but they have a supplier who has them. I had to buy a different mounting bracket though, as the new LNB had a larger throat like the offset LNBs

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