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Sky Digital BSkyB, Freesat & Saorsat support forum
Sky & Freesat fringe reception
Astra 2E & 2F: Sidelobes, Nulls and Spots
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<blockquote data-quote="gambit" data-source="post: 859338" data-attributes="member: 304438"><p>The 2nd map, "the 2E UK Spot Shifted 15 degrees East", is simply the predicted 2F UK spot footprint but shifted 15 degrees east. You cannot use that map to predict reception in southern Spain once the satellite moves to 28.2 east.</p><p></p><p>To receive a transmission you have to be well away from a side-lobe. The signal is so weak once you are outside the primary lobe that you have to be almost midway between the nulls at the peak of the side-lobe, as you are in Valencia.</p><p></p><p></p><p></p><p>I do not know what algorithm was used to compute the footprint. I expect it uses a calculation based on a circular dish. The algorithm must use the physics of diffraction patterns given that the pattern of a central peak and side lobes is a diffraction pattern. The pattern for a circular aperture depends only on the dish diameter and the frequency.</p></blockquote><p></p>
[QUOTE="gambit, post: 859338, member: 304438"] The 2nd map, "the 2E UK Spot Shifted 15 degrees East", is simply the predicted 2F UK spot footprint but shifted 15 degrees east. You cannot use that map to predict reception in southern Spain once the satellite moves to 28.2 east. To receive a transmission you have to be well away from a side-lobe. The signal is so weak once you are outside the primary lobe that you have to be almost midway between the nulls at the peak of the side-lobe, as you are in Valencia. I do not know what algorithm was used to compute the footprint. I expect it uses a calculation based on a circular dish. The algorithm must use the physics of diffraction patterns given that the pattern of a central peak and side lobes is a diffraction pattern. The pattern for a circular aperture depends only on the dish diameter and the frequency. [/QUOTE]
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Sky Digital BSkyB, Freesat & Saorsat support forum
Sky & Freesat fringe reception
Astra 2E & 2F: Sidelobes, Nulls and Spots
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