Usually called a parabolic, the correct geometric term is a paraboloid. This reflector antenna is the only practical choice when gains above 25 dBi are required.
TV dish antennas are used for satellite reception both for C-band (requiring an 8-foot dish) and Ku-band. DirecTV, Dish Network, and Voom all use Ku-band, and their satellites are powerful enough that an 18-inch dish is adequate except in Alaska.
A couple tree leaves are enough to disrupt Ku-band reception. But diffraction has little effect on the signal path. If there were a 20-inch diameter hole through the crown of the tree, and if the dish could be pointed at the satellite through that hole, then the tree would have no effect on reception (until the wind blew).
Dish antennas
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