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DISH SETUP: Single sat, Multi-Sat & Motorised
Re- Installing Motorised Dish
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<blockquote data-quote="2old4this" data-source="post: 5894" data-attributes="member: 174998"><p>Nice history, good info!</p><p></p><p>On the polarisor thing, perhaps I should have been clearer in my use of the term "LNB".</p><p></p><p>Here's my understanding of the situation:</p><p></p><p>Indeed there is no correlation between the actual LNB and a polarisation system in a satellite system. That is, the LNB itself (as distinct from the polarisor) is not in some way tailored to the incoming signal's polarisation - since it only ever has to distinguish H or V (the circular polarisation being viewed as H/V components, or else having been depolarised to H/V by a dielectric plate).</p><p></p><p>But my point was relating to the need for the polarisor to be skewable if one wants to view linearly- and circularly- polarised sigals using one "unit" (let's call it that, rather than "LNB"). If the polarisor is NOT skewable (as is the case for the fixed probes in a Universal LNB, for example) then it will not be possible to receive the circularly-polarised signals depolarised by the dielectric as well as the originally linearly-polarised signals (since with the dielectric optimally oriented, they end up at 45 degrees to each other at the polarisor).</p><p></p><p>If I am misunderstanding something, could you please make the necessary corrections/additions to the circular polarisation FAQ I wrote recently:</p><p>http://www.satellites.co.uk/scripts/webforum/DCForumID20/76.html</p><p></p><p></p><p>By the way, this (interesting) disssion arose because you stated that no new digital systems support magnetic polarisors. And you went on to state that to use one would hinder the reception of MPEG. </p><p>Can you explain what the issue there is? Why would a magnetic polarisor be a problem, but not an electro-mechanical one? </p><p></p><p>2old</p></blockquote><p></p>
[QUOTE="2old4this, post: 5894, member: 174998"] Nice history, good info! On the polarisor thing, perhaps I should have been clearer in my use of the term "LNB". Here's my understanding of the situation: Indeed there is no correlation between the actual LNB and a polarisation system in a satellite system. That is, the LNB itself (as distinct from the polarisor) is not in some way tailored to the incoming signal's polarisation - since it only ever has to distinguish H or V (the circular polarisation being viewed as H/V components, or else having been depolarised to H/V by a dielectric plate). But my point was relating to the need for the polarisor to be skewable if one wants to view linearly- and circularly- polarised sigals using one "unit" (let's call it that, rather than "LNB"). If the polarisor is NOT skewable (as is the case for the fixed probes in a Universal LNB, for example) then it will not be possible to receive the circularly-polarised signals depolarised by the dielectric as well as the originally linearly-polarised signals (since with the dielectric optimally oriented, they end up at 45 degrees to each other at the polarisor). If I am misunderstanding something, could you please make the necessary corrections/additions to the circular polarisation FAQ I wrote recently: http://www.satellites.co.uk/scripts/webforum/DCForumID20/76.html By the way, this (interesting) disssion arose because you stated that no new digital systems support magnetic polarisors. And you went on to state that to use one would hinder the reception of MPEG. Can you explain what the issue there is? Why would a magnetic polarisor be a problem, but not an electro-mechanical one? 2old [/QUOTE]
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DISH SETUP: Single sat, Multi-Sat & Motorised
Re- Installing Motorised Dish
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