There's this very beautiful software called MMANA-GAL, that lets you model radiation patterns of antennas.

By beautiful, I very much mean that it's beautiful below the surface. Visually it looks awful, and it's not very easy to use. But it's very very good.

I've been using it to try to design a highly-directional foldable Yagi-Uda antenna, for use with a handheld #hamradio. If I can get the impedance right, MMANA-GAL says it could have around 13.3dBi of gain, which is to say that signals in the "best" direction are about 20x stronger than if you instead used a hypothetical perfectly spherical antenna.

And the design is basically made of 10 wires, sewn into a 1m square piece of fabric. I'm pretty excited about this, because if it works it should be really easy to carry around in a backpack (~as unwieldy as a t-shirt), and it will mean that you should be able to use a teeny 5W radio to communicate over really long distances (as long as you know which direction you want to talk). I've seen someone make something like this that let him use such a radio to communicate nearly 100mi! Normally these radios can communicate at most 10mi.