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Satellite TV receivers & systems support forums
DISH SETUP: Single sat, Multi-Sat & Motorised
Av-Comm C Band Waveguide Polariser and a Zinwell Dual Polarity C Band LNBF,
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<blockquote data-quote="moonbase" data-source="post: 1117821" data-attributes="member: 178786"><p>Spiff,</p><p></p><p>At 560mm you are 14mm further away from the dish than the focal length.</p><p></p><p>From my limited knowledge of dish geometry and feed alignment you need the opening rim of the polo pipe to be at a distance that is less than the focal length.</p><p>The logic is to get the focal length of the dish to a point inside the polo pipe at a depth whereby the polo pipe is at a distance to be fully illuminated by the dish but close enough not to be gathering noise from ouside the surface of the dish.</p><p></p><p>My general starting point settings are to secure the polo pipe so that the opening rim nearest to the dish is 5mm less than the focal length of the dish and place the scalar so that the edge of scalar concentric rings is 20mm from the opening rim of the polo pipe. This gives 20mm of polo pipe protruding from the scalar.</p><p></p><p>You might find that you are restricted in how far back you can slie the scalar along the polo pipe due to the amount the polo pipe has been turned down at the scalar end.</p><p>I had my polo pipe modified by getting an additional length turned down on the scalar end to provide more backward adjustment with the scalar.</p></blockquote><p></p>
[QUOTE="moonbase, post: 1117821, member: 178786"] Spiff, At 560mm you are 14mm further away from the dish than the focal length. From my limited knowledge of dish geometry and feed alignment you need the opening rim of the polo pipe to be at a distance that is less than the focal length. The logic is to get the focal length of the dish to a point inside the polo pipe at a depth whereby the polo pipe is at a distance to be fully illuminated by the dish but close enough not to be gathering noise from ouside the surface of the dish. My general starting point settings are to secure the polo pipe so that the opening rim nearest to the dish is 5mm less than the focal length of the dish and place the scalar so that the edge of scalar concentric rings is 20mm from the opening rim of the polo pipe. This gives 20mm of polo pipe protruding from the scalar. You might find that you are restricted in how far back you can slie the scalar along the polo pipe due to the amount the polo pipe has been turned down at the scalar end. I had my polo pipe modified by getting an additional length turned down on the scalar end to provide more backward adjustment with the scalar. [/QUOTE]
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Satellite TV receivers & systems support forums
DISH SETUP: Single sat, Multi-Sat & Motorised
Av-Comm C Band Waveguide Polariser and a Zinwell Dual Polarity C Band LNBF,
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