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I’m sure many who would like to venture in D-I-Y FTA satellite setups have often wondered how to achieve a multi-LNB set-up like the one above. Well, wonder no more. Below is the formula one would use to determine the spacing between any two LNBs. I’ll use a 240cm prime focus dish in this example but it works for any dish size.
[FONT=Tahoma]Step 1.[/FONT]
M = (H/2) + { (D * D)/ (8 * H)
where D = diameter, H = depth.
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For a 240cm pf dish, D = 240cm, H = 39.344cm.
M = (39.344/2) + { (240 * 240) / (8 * 39.344) }
= [I]202.67322.[/I]
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[FONT=Tahoma]Step 2.[/FONT]
Focal Length (F) = (D * D) / (16 * H)
= (240 * 240) / (16 * 39.344)
= [I]91.50061[/I].
Step 3.
Calculate the value of N.
N = M - F
= 202.67322 - 91.50061
= 111.17261.
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Step 4.
Calculate the LNB gap between any two satellites e.g. between IntelSat 10-02 @1W and Eutelsat 10A @ 10E.
The gap in degrees between these two satellites is 11.
Tan of angle 11 degrees (T) = 0.1944
Gap between the two LNBs = N * T
= 111.17261 * 0.1944
= [I]21.6120 cm[/I]
= approx. 21.61cm. This gap is measured between the centre points of the two LNBs.
Happy hunting, satmates.
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