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Satellite Systems - What to Buy - What to install
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<blockquote data-quote="hdp160" data-source="post: 803915" data-attributes="member: 189308"><p>Ultimate sweet spot umm.</p><p></p><p>LNB manufacturers often give conflicting advice. </p><p>The debate goes along the lines of either:-</p><p></p><p>1. At the surface of the "transparent" front face of the LNB.</p><p></p><p>or </p><p></p><p>2. Just behind it at a distance directly related to the dish size.</p><p>(This is further complicated by non-circular dishes)</p><p></p><p>The argument (BTW I am NOT agreeing this ONLY reporting!) is that the aperture behind the "transparent" weather cover has a manufactured diameter which accepts reflected waves from all over the dish (and off all frequencies) and the waves from the outer edge compared to those nearer the centre produce a "fuzzy" focus within the feed horn. </p><p></p><p>The bouncing waves within the feed horn have microscopically different wave lengths obviously. A well designed feed horn dimensions are calculated at the mid point of the frequencies expected </p><p></p><p>You are only talking about a few hundred micrometers.</p><p></p><p>Ideally the convergence of the reflected waves (mid band) should be on or very near the probes.</p><p></p><p>So I agree ....the sweet spot is where a piece of paper catches fire on a sunny day.........<grin></p></blockquote><p></p>
[QUOTE="hdp160, post: 803915, member: 189308"] Ultimate sweet spot umm. LNB manufacturers often give conflicting advice. The debate goes along the lines of either:- 1. At the surface of the "transparent" front face of the LNB. or 2. Just behind it at a distance directly related to the dish size. (This is further complicated by non-circular dishes) The argument (BTW I am NOT agreeing this ONLY reporting!) is that the aperture behind the "transparent" weather cover has a manufactured diameter which accepts reflected waves from all over the dish (and off all frequencies) and the waves from the outer edge compared to those nearer the centre produce a "fuzzy" focus within the feed horn. The bouncing waves within the feed horn have microscopically different wave lengths obviously. A well designed feed horn dimensions are calculated at the mid point of the frequencies expected You are only talking about a few hundred micrometers. Ideally the convergence of the reflected waves (mid band) should be on or very near the probes. So I agree ....the sweet spot is where a piece of paper catches fire on a sunny day.........<grin> [/QUOTE]
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