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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="Breadfan" data-source="post: 101265" data-attributes="member: 189184"><p>Hi,</p><p></p><p>I'm back in the game again with a shiny new Channel Master 90cm dish, which will hopefully go up by the weekend if the wind will drop off a little!</p><p></p><p>I'm combining the dish with an Invacom c120 / CM feedhorn and I'm not sure how to find the exact focal point so I know how far from the face to site the feedhorn. I've searched all over but no joy, the CM/Andrew website wasn't particularly helpful at all : (</p><p></p><p>Ok, I know the formula is this :-</p><p></p><p>F = (DxD) / 16d, where D is dish diamter and d is depth</p><p></p><p>Problem is, the dish isn't perfectly round. Horizontally it's about 91cm wide and 9cm deep, making 'F' about 57.5cm. Vertically it's more like 98cm and 8.5cm, making 'F' about 70.5cm !!!</p><p></p><p>That's quite a big difference and being a perfectionist I need to know where it should be !! Does anybody know which is correct, or do I use another measurement (diagonal?) </p><p></p><p>Better still, has anybody got the official focal distance recommended for this dish?</p><p></p><p>I suppose I can just experiment with signal levels when it's up and running : )</p><p></p><p>Thanks,</p><p>Breadfan</p></blockquote><p></p>
[QUOTE="Breadfan, post: 101265, member: 189184"] Hi, I'm back in the game again with a shiny new Channel Master 90cm dish, which will hopefully go up by the weekend if the wind will drop off a little! I'm combining the dish with an Invacom c120 / CM feedhorn and I'm not sure how to find the exact focal point so I know how far from the face to site the feedhorn. I've searched all over but no joy, the CM/Andrew website wasn't particularly helpful at all : ( Ok, I know the formula is this :- F = (DxD) / 16d, where D is dish diamter and d is depth Problem is, the dish isn't perfectly round. Horizontally it's about 91cm wide and 9cm deep, making 'F' about 57.5cm. Vertically it's more like 98cm and 8.5cm, making 'F' about 70.5cm !!! That's quite a big difference and being a perfectionist I need to know where it should be !! Does anybody know which is correct, or do I use another measurement (diagonal?) Better still, has anybody got the official focal distance recommended for this dish? I suppose I can just experiment with signal levels when it's up and running : ) Thanks, Breadfan [/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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