After playing with Arduino and different kind of sensors for my garden, now I'm starting a new project for my free time.
I want to work with RF communications because I need a long range device for my application, about 2 Km distance.
The idea is to make only an identification of which unit is, as a long range RFID but without RFID.
I mean some devices/units are placed somewhere, and after a time, someone could move them to another place, so I want to know where they are, only reading information send by them via RF. I don't mind their real position (GPS) because I going to be able to see them where they are from my top window. I only want to know which of them are.
- I'm reading about 315/434 MHz, but it seems not be able to get this distance without a high power consumption.
What about a lower frequency (150 MHz)? It is above the license frequency band for AM/FM radios.
- I live in a village - I have a lot of terrain to play with my experiments and a line of sight over 2 Km.
The @Hoppo idea is just what I'm trying to do. Also it lets me to get "energy harvesting" because the idea is transmitters go with a small battery.
Also the transmitters have to be small enough and without antennas for not disturbing and avoid dogs play with them.
In receiver side, it doesn't matter if I need a larger antenna or more power. It will go connected directly to a PC or power source.
Moreover as @Hoppo says, I only want to send a 'ping', a message with an identifier and maybe battery level, so data rates could be lower than 9600bps.