Log in
Register
Menu
Log in
Register
Home
What's new
Latest activity
Authors
Forums
New posts
Search forums
What's new
New posts
Latest activity
Members
Current visitors
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Forums
Satellite TV receivers & systems support forums
DISH SETUP: Single sat, Multi-Sat & Motorised
Usals problem & alignment
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="a33" data-source="post: 1085355" data-attributes="member: 332642"><p>I just checked on the geometry of an offset dish:</p><p></p><p><strong>When <em>the elevation rotation axis </em>of an AzEl mount is situated exactly in line with the line Center of dish face (C') to Deepest point of the dish (D),</strong> so that it lies <strong>exactly at the beam center line</strong>, then the received satellite beam of an inverted offset dish <strong>is exactly at the same height</strong> as that of a normally mounted offset dish.</p><p><em>See the attached picture, with the lines C' - D exactly in line, for both normal and inverted setup.</em></p><p></p><p>When the axis is situated higher up, e.g. behind the deepest point or behind the center of the dish, the inverted dish receives a HIGHER part of the beam. So in that case inverted mounting is advantageous: the higher the elevation axis is situated, the more advantageous.</p><p>This goes for a fixed mast, and also for a motor setup.</p><p></p><p>How much higher? For a fixed mast this could be calculated, with inputs:</p><p>1) distance dish face to elevation axis</p><p>2) distance top of dish to height of the axis (measured at dish face)</p><p>3) height of the dish</p><p>4) offset angle of the dish (or width of the dish, in combination with 3.)</p><p>Alas, 1 and 2 are not measured very easily (but not impossible!). So I'll leave the making of the formula to another time, or another person.</p><p></p><p>For a motor setup, the advantage diminishes the further you go from due south or due north, I assume. But I think even with a 90 degrees motor rotation, you would still have more than half of the advantage, I think.</p><p>But I'm not sure; I have difficulty to visualize the consequences of dish inversion in that situation. It might be dependant on the MOTOR-axis elevation angle, so on your site latitude, if I'm not mistaken.</p><p></p><p></p><p>On a motorized setup with a bend in the shaft, you can add an extra effect by changing the angle of the shaft bend, as Trust showed.</p><p>By that, the position of the dish elevation rotation axis <em>relative to the height of the mast</em> gets higher than in 'normal' position.</p><p>That would be the new starting point for the dish's elevation rotation axis, so there is your advantage...</p><p></p><p></p><p>I hope I've helped to clear things up a bit about the principle(s),</p><p></p><p>Greetz,</p><p>A33</p><p></p><p></p><p>[ATTACH=full]129115[/ATTACH]</p></blockquote><p></p>
[QUOTE="a33, post: 1085355, member: 332642"] I just checked on the geometry of an offset dish: [B]When [I]the elevation rotation axis [/I]of an AzEl mount is situated exactly in line with the line Center of dish face (C') to Deepest point of the dish (D),[/B] so that it lies [B]exactly at the beam center line[/B], then the received satellite beam of an inverted offset dish [B]is exactly at the same height[/B] as that of a normally mounted offset dish. [I]See the attached picture, with the lines C' - D exactly in line, for both normal and inverted setup.[/I] When the axis is situated higher up, e.g. behind the deepest point or behind the center of the dish, the inverted dish receives a HIGHER part of the beam. So in that case inverted mounting is advantageous: the higher the elevation axis is situated, the more advantageous. This goes for a fixed mast, and also for a motor setup. How much higher? For a fixed mast this could be calculated, with inputs: 1) distance dish face to elevation axis 2) distance top of dish to height of the axis (measured at dish face) 3) height of the dish 4) offset angle of the dish (or width of the dish, in combination with 3.) Alas, 1 and 2 are not measured very easily (but not impossible!). So I'll leave the making of the formula to another time, or another person. For a motor setup, the advantage diminishes the further you go from due south or due north, I assume. But I think even with a 90 degrees motor rotation, you would still have more than half of the advantage, I think. But I'm not sure; I have difficulty to visualize the consequences of dish inversion in that situation. It might be dependant on the MOTOR-axis elevation angle, so on your site latitude, if I'm not mistaken. On a motorized setup with a bend in the shaft, you can add an extra effect by changing the angle of the shaft bend, as Trust showed. By that, the position of the dish elevation rotation axis [I]relative to the height of the mast[/I] gets higher than in 'normal' position. That would be the new starting point for the dish's elevation rotation axis, so there is your advantage... I hope I've helped to clear things up a bit about the principle(s), Greetz, A33 [ATTACH type="full"]129115[/ATTACH] [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Satellite TV receivers & systems support forums
DISH SETUP: Single sat, Multi-Sat & Motorised
Usals problem & alignment
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
Accept
Learn more…
Top