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© Copyright 1998, Jim Loy
Why are there hundreds of holes in some satellite dishes? A satellite dish is not an antenna, it is a reflector. The antenna is at the end of that arm that sticks out from the dish. The antenna is at the focal point of the dish. The dish reflects microwaves, just as a mirror reflects light. Microwaves are defined to be radio waves with wavelengths of from 5 mm. to 30 cm. Radio waves are electro-magnetic waves, just like light, but with a much longer wavelength. Such a wave cannot go through a hole smaller than its wavelength. Apparently all of the TV signals coming from satellites are of longer wavelength than the holes that you see in some dishes. So, even though you can see through a dish, the appropriate radio waves reflect from the dish, as if it were solid.
Since holes do not hurt in any way, they can be used to lighten the dish, and make it less expensive.
Apparently, Arthur C. Clark invented the communication satellite, back before Sputnik, in one of his science fiction stories. He never patented it, though.