from “is it directional? how cheap could you make a big antenna?”<div dir="auto"><br></div><div dir="auto">i am not a radio engineer.</div><div dir="auto"><br></div><div dir="auto">satellite dishes use the reflection of metal to focus signals onto a receptor.</div><div dir="auto">the curved shape behind them is analogous to the lens of the eye, bending the radiation differently depending on what part it strikes.</div><div dir="auto"><br></div><div dir="auto">usually they are designed to focus parallel radiation from an effectively infinitely distant source in outer space (with a parabolic shape). they can instead be designed to focus emission from a specific arbitrarily located relative fixed point at a specific arbitrary distance (with a spherical shape). the two curves are physically similar but focus differently.</div><div dir="auto"><br></div><div dir="auto">they could also surface soft or hinged material so as to change how they focus live. this would be analogous to how the muscles of the eye reshape the lens so as to focus near or far.</div><div dir="auto"><br></div><div dir="auto">similarly you could put an array of sensors at the receptor rather than a single one. high-end radio telescopes do this, outputting a small count of pixels rather than a single signal. these are analogous to the retina, the array of receptors in the back of the eye.</div><div dir="auto"><br></div><div dir="auto">once you put two of them next to each other on gymbals, the stereoscopic vision you are making analogy to is possibly what radio astronomers do to triangulate distances from two different locations — but if your reflectir is bending itself to focus on something near rather than far you are doing something a little different.</div><div dir="auto"><br></div><div dir="auto">[…]</div>