Schematic diagram of a parabolic reflector. Incoming sound is directed to the microphone placed at the focus of the parabola-shaped reflector. The property of the parabolic shape to reflect all sound ...

Parabolic reflectors are pretty handy devices. Whether you’re building a microwave antenna or a long-distance directional microphone, suitable commercial dishes aren’t that hard to come by.

To me, this means a large parabolic reflector, a feed horn made of brass sheet, coat hanger wire, and at least for the initial experiments, an RTL-SDR dongle. I’ve done the calculations ...