Why not just get a HAM radio? Heck of a lot better range. A global standard. Many orders of magnitude more users. And some of those users are technical enough to be able to fix their own radio if it broke.

Even a GMRS or FRS radio would be better. Heck, even a CB radio would top it.

With a good set of lungs, you could probably make a megaphone, like cheerleaders use, top it. A signal mirror and Morse Code ... a log drum and some sticks ... a smoky fire with a blanket to shape the smoke signals ... lots of things would top it.

This gadget has about as much real-world utility as an insulated pencil. Why would you want an insulated pencil? My point exactly!