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Sky Digital BSkyB, Freesat & Saorsat support forum
Sky & Freesat fringe reception
Offset v prime focus chat
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<blockquote data-quote="ralphmagno" data-source="post: 781394" data-attributes="member: 189146"><p>ok my bad on the lnb.</p><p>you can not use the same lnb on a prime and offset.</p><p>but looking at winkapidia here is what it says.</p><p>4 types of dishes </p><p>prime focus has the least gain efficency at 55% to 60%, this is due to lnb shadowing the dish and support arms and blocking some signal.</p><p></p><p>next offset , this has 60% to 65% and is used in direct to home apps.</p><p></p><p>cassegrain is running about 65% to70% and this is used for up links and down links as well.</p><p></p><p>the last is gregorian this can have as much as 70%</p><p></p><p>if we are grabing as much gain in week areas we would want the last two.</p><p>SETI and deep space setups do not use the first two at all.</p><p>they want as much gain as possible.</p><p></p><p>judging by this a 2 meter offset would be better than a 2 meter prime. and a 2 meter gregorian would be the best.</p><p>now this is excluding the feed horn type and lnb gain and noise figure as well an the cross modulation of the lnb.</p><p>ralph:-righton</p></blockquote><p></p>
[QUOTE="ralphmagno, post: 781394, member: 189146"] ok my bad on the lnb. you can not use the same lnb on a prime and offset. but looking at winkapidia here is what it says. 4 types of dishes prime focus has the least gain efficency at 55% to 60%, this is due to lnb shadowing the dish and support arms and blocking some signal. next offset , this has 60% to 65% and is used in direct to home apps. cassegrain is running about 65% to70% and this is used for up links and down links as well. the last is gregorian this can have as much as 70% if we are grabing as much gain in week areas we would want the last two. SETI and deep space setups do not use the first two at all. they want as much gain as possible. judging by this a 2 meter offset would be better than a 2 meter prime. and a 2 meter gregorian would be the best. now this is excluding the feed horn type and lnb gain and noise figure as well an the cross modulation of the lnb. ralph:-righton [/QUOTE]
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Sky Digital BSkyB, Freesat & Saorsat support forum
Sky & Freesat fringe reception
Offset v prime focus chat
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