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Apr 18th, 2011 at 2:29pm
If you have an offset feed design, with feed arm at the bottom, get your head under the rear lower edge of the dish just beside the back end of the feed support arm and look along the lower edge of the cylindrical beam. The lower edge of the cylindrical beam, goes approx via the top of the feed horn window. The beam diameter is the same as the dish diameter for some distance (*). Ideally put a thin strip of wood under the lower edge of the dish next to the feed arm. Put an inclinometer on it and set it to the beam elevation anlge. Look along the wood. Can you see the sky ?
Best regards, Eric.
(*) Distance = 0.2 x d x d / wavelength, where d = dish diameter (m). Wavelength = 0.03 m at 10 GHz. Beyond the distance the beam diverges (gets wider)
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