I have two XBEE 900HP S3B modules with 2dBi dipole antennas on them. I have accomplished communication between them when working in my house, but I need to get communication of about 3 or 4 km (1.8 to 2.5 miles) in urban places. This cards have a maximum range of about 28 miles with LOS using high gain antennas.
So I want to know what do you recommend me to get this working on urban areas with a range of 4 km. It is possible to change the transmission power to its maximum? How much gain is "high-gain" for an antenna? What other changes must I do to get this working?
Thank you very much