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DISH SETUP: Single sat, Multi-Sat & Motorised
Dish Setup Guides, Information threads and FAQs
Multifeed installation and exact calculation of LNB position
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<blockquote data-quote="a33" data-source="post: 958970" data-attributes="member: 332642"><p>Well, I studied the artice by Marco Terada quite a bit, but I couldn't find that he concludes that point P in the picture (above the center of the dish) gives highest gain.</p><p>Point P in the picture, I believe, is introduced as a variable point to the question where to aim the feed. He writes:</p><p></p><p><em>“If the feed remains pointed at the apex of the parent paraboloid (i.e., psi-f = 0 degrees), negligible XPOL is generated (15). However, this leads to large spillover and associated gain loss. Therefore, in practice the feed is tilted to direct its pattern toward the reflector, resulting in the introduction of high XPOL.”</em></p><p><em>“It is worth noting that cross polarization (in linear polarized feed, A33) arises from the reflector curvature and <strong>from the tilting of the feed</strong>.” (the higher the tilt, the higher the XPOL; See figure 9 of the pdf, A33)</em></p><p><em></em></p><p><strong><em>“In many systems, the feed pointing angle psi-f is set equal to the angle that bisects the reflector, psi-B , or to the angle pointed toward the center of the projected aperture, psi-C .” </em></strong></p><p><em>[Point C, the center of projected aperture, would by the way also be <strong>below</strong> the center of the dish, if I project correctly, A33]</em></p><p></p><p>As I read this article, the recommendation to have the least spillover and not too much XPOL would be: <u><strong>aiming below the center of the dish</strong></u>; to point B (G-spot) or point C in the picture!</p><p></p><p></p><p>So as far as I'm concerned: the G-spot holds its preferred position. </p><p>And also the 'horizontal G-spots' (as I called them) for aiming multiple LNBs on multifeed brackets!</p><p></p><p>Thanks for the link to this interesting though not easy article.</p><p></p><p>Greetz,</p><p>A33</p></blockquote><p></p>
[QUOTE="a33, post: 958970, member: 332642"] Well, I studied the artice by Marco Terada quite a bit, but I couldn't find that he concludes that point P in the picture (above the center of the dish) gives highest gain. Point P in the picture, I believe, is introduced as a variable point to the question where to aim the feed. He writes: [I]“If the feed remains pointed at the apex of the parent paraboloid (i.e., psi-f = 0 degrees), negligible XPOL is generated (15). However, this leads to large spillover and associated gain loss. Therefore, in practice the feed is tilted to direct its pattern toward the reflector, resulting in the introduction of high XPOL.” “It is worth noting that cross polarization (in linear polarized feed, A33) arises from the reflector curvature and [B]from the tilting of the feed[/B].” (the higher the tilt, the higher the XPOL; See figure 9 of the pdf, A33) [/I] [B][I]“In many systems, the feed pointing angle psi-f is set equal to the angle that bisects the reflector, psi-B , or to the angle pointed toward the center of the projected aperture, psi-C .” [/I][/B] [I][Point C, the center of projected aperture, would by the way also be [B]below[/B] the center of the dish, if I project correctly, A33][/I] As I read this article, the recommendation to have the least spillover and not too much XPOL would be: [U][B]aiming below the center of the dish[/B][/U]; to point B (G-spot) or point C in the picture! So as far as I'm concerned: the G-spot holds its preferred position. And also the 'horizontal G-spots' (as I called them) for aiming multiple LNBs on multifeed brackets! Thanks for the link to this interesting though not easy article. Greetz, A33 [/QUOTE]
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Satellite TV receivers & systems support forums
DISH SETUP: Single sat, Multi-Sat & Motorised
Dish Setup Guides, Information threads and FAQs
Multifeed installation and exact calculation of LNB position
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