What is legal in your country ?
If you buy something on Ebay, that tells "2km range", it might be just 500 meters.
In my country the Walkie-talkie at 446 MHz is legal to use without license. Those can have a range of a few kilometers. But I don't know if it is allowed to send digital data with them.
You find a lot information if you google for: arduino long range rf
First of all, thanks for your reply.
In my country it is legal to use 400-460MHZ, no problem. This is for a project, they recommend us to use this kind of frequency, so i think that there isn't any problem. As i already mentioned, it will be used to send gyro, accelerometer, gps and pressure info to the base controler. FOr the 1.5km what is the most recommend rf module (the one that has more support, tutorials, etc)?