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Satellite TV receivers & systems support forums
DISH SETUP: Single sat, Multi-Sat & Motorised
Tests of 120cm antennas
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<blockquote data-quote="RimaNTSS" data-source="post: 929206" data-attributes="member: 312276"><p>Back to topic: So I have finished measurements and do not think I can do any better for this CM 1,2m dish. </p><p>Used laser to see where LNB is pointed and digital protractor to measure angles [ATTACH]78900[/ATTACH] . Leaning of line from F towards dish was 66,3*, line A-B was 1,8*, that means angle between those 2 lines is 64,5*. Remeasured more carefully lines A-F and B-F got 1224 and 714mm. Therefore original LNB holder holds LNB in such a way that it's Phase Center is only 7mm from Focal point of the dish (pink line =7mm) [ATTACH]78902[/ATTACH] . What spoils everything is direction of the LNB, so line from LNB hits the surface of the dish 126mm higher than it should be doing that. One could think, OK, we should lean LNB little bit lower and than it will be pointed to the right direction and issue will be solved! Bright idea, but will not work like that. If we lean LNB more down than it's Phase Center will also go more down, so situation will be even worse. To solve the issue, I suggest to make another LNB holder and then you will improve system performance at about 5%, which is more or less equivalent of increasing dish size for about 10-15cm. </p><p>On the drawing everything colored blue is calculated, everything in green- carefully measured [ATTACH]78901[/ATTACH] . That is all for today folks. ;)</p></blockquote><p></p>
[QUOTE="RimaNTSS, post: 929206, member: 312276"] Back to topic: So I have finished measurements and do not think I can do any better for this CM 1,2m dish. Used laser to see where LNB is pointed and digital protractor to measure angles [ATTACH]78900[/ATTACH] . Leaning of line from F towards dish was 66,3*, line A-B was 1,8*, that means angle between those 2 lines is 64,5*. Remeasured more carefully lines A-F and B-F got 1224 and 714mm. Therefore original LNB holder holds LNB in such a way that it's Phase Center is only 7mm from Focal point of the dish (pink line =7mm) [ATTACH]78902[/ATTACH] . What spoils everything is direction of the LNB, so line from LNB hits the surface of the dish 126mm higher than it should be doing that. One could think, OK, we should lean LNB little bit lower and than it will be pointed to the right direction and issue will be solved! Bright idea, but will not work like that. If we lean LNB more down than it's Phase Center will also go more down, so situation will be even worse. To solve the issue, I suggest to make another LNB holder and then you will improve system performance at about 5%, which is more or less equivalent of increasing dish size for about 10-15cm. On the drawing everything colored blue is calculated, everything in green- carefully measured [ATTACH]78901[/ATTACH] . That is all for today folks. ;) [/QUOTE]
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Satellite TV receivers & systems support forums
DISH SETUP: Single sat, Multi-Sat & Motorised
Tests of 120cm antennas
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