We are currently working on a project using 3 XBee modules. One is like a data center or the master of the other two XBees.
We did a range test with a master and a slave XBee on an open field using a router antenna which is 3 dBi and is dipole. The distance we had was roughly 30 meters from the master. We ordered an omnidirectional 7 dBi car antenna with 2.5 meters wire length and again repeated our range test using it. The result was better but we just reached 800 meters.
Our project needs to get about 15 km. Will we be able to obtain it? We tried using an RF amplifier but it doesn't seem to work well with XBee modules. I have read articles/forums on the internet that uses a 2.5 dBi dipole antenna and they are able to obtain kilometer values on their range test. I don't know where we went wrong. I did my research but I cannot reach our desired output.