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Satellite TV receivers & systems support forums
DISH SETUP: Single sat, Multi-Sat & Motorised
Calculating Focal Point ?
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<blockquote data-quote="steffan_st" data-source="post: 101358" data-attributes="member: 177727"><p>This is copied and pasted from a post by a guy called Benny at satdudez a while ago,maybe it can help you:</p><p></p><p>I thought I should inform about my findings and perhaps some of you like to check your own dishes chasing the last dBs.</p><p></p><p>The empiric formula for fokal distance (f) in offset antennas is f = (D x D)/(16 x d).</p><p>Where D is the width and d is the deepest measure from your edges down to dish surface. When you measure the width you should only measure the curved part. The height you dont measure.</p><p></p><p>When you have calculated f, you attach a plastic string or similar to the bottom edge of your dish. You make a mark or a knot on the string at distance f from the edge. The loose end of the string shall be attached to the upper edge of your dish. There are some guesses that can be made how long the string shall be from the knot or mark to the upper edge, but I think it is better to search the focal point with this distance flexible. You can take 1.8 x f to start with if you like to have some idea of how long string you need.</p><p></p><p>You shall not be surprised if you find that your present position gives you the strongest signal. That is what you worked for when installing. To check if you have the proper focal point higher or lower you must also change the elevation of your dish until you again get a strong signal to compare with. Elevate if you lift the focal point.</p></blockquote><p></p>
[QUOTE="steffan_st, post: 101358, member: 177727"] This is copied and pasted from a post by a guy called Benny at satdudez a while ago,maybe it can help you: I thought I should inform about my findings and perhaps some of you like to check your own dishes chasing the last dBs. The empiric formula for fokal distance (f) in offset antennas is f = (D x D)/(16 x d). Where D is the width and d is the deepest measure from your edges down to dish surface. When you measure the width you should only measure the curved part. The height you dont measure. When you have calculated f, you attach a plastic string or similar to the bottom edge of your dish. You make a mark or a knot on the string at distance f from the edge. The loose end of the string shall be attached to the upper edge of your dish. There are some guesses that can be made how long the string shall be from the knot or mark to the upper edge, but I think it is better to search the focal point with this distance flexible. You can take 1.8 x f to start with if you like to have some idea of how long string you need. You shall not be surprised if you find that your present position gives you the strongest signal. That is what you worked for when installing. To check if you have the proper focal point higher or lower you must also change the elevation of your dish until you again get a strong signal to compare with. Elevate if you lift the focal point. [/QUOTE]
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Satellite TV receivers & systems support forums
DISH SETUP: Single sat, Multi-Sat & Motorised
Calculating Focal Point ?
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