I've a project that I'm working on that requires long-range (10-ish km), mostly one-way communication at low data rates (100 baud is fine). Imagine a one-to-many remote switch. The transmitter will be centralized; but the receivers are many, scattered, and must be as small and low-power as possible. I've thought about doing a CW transmitter and stupid-simple RF detector for receive. But the problems with that is that (a) there could be other people on the band (915 MHz ISM) that I don't want to bump in to and a big honking CW transmitter would be a pain to them; and (b) that I may in the future want to add limited Tx capability to the other (currently receive-only) end as well. And so may as well build in that capability in the beginning.
So my question is this: Is LoRa the right thing for me to be looking at? Is there an easier way to do it? If I can get the receivers down to thumbnail size, I'll be happy.
So sorry if this has been covered before. I'm a true newbie to this and have only been thinking about it for a week or so. Any help or suggestions are appreciated. Thanks!
Edit: Just an FYI - I'm thinking NavSpark Mini and a HopeRF board to get the size that I need.