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Showing posts from November, 2018

Care and Feeding of a Parabolic Reflector

If you want to listen to Jupiter sing , bounce a message off the Moon , or bounce off aircraft , random space junk , or meteor trails , talk to a Satellite , or a little unmanned Aircraft , you need a very high gain antenna.  An easy way to make one, is from an old C-band satellite TV, Big Ugly Dish (BUD). Considering that the amount of space junk is ever growing, Junk Bounce Communications (TM) can only improve.  An advantage of Junk Bounce is that it works at any frequency, from UHF up to K-band, so orbiting space junk could become the new ionosphere, a neat radio wave reflector around the planet! To use an unknown dish, you need to find its focal point and then make a little antenna with a good front to back ratio, to use as a feed. Focal Length The focal point of a parabola is easy to find using some forgotten high school geometry: Measure the diameter (D) and the depth (d) of the dish. The focal length F = D^2 / 16 x d Note that an offset feed dish is only half