The first thing to do is to make sure the antenna is correctly designed and connected. Is the module and PCB layout correctly designed per the module datasheet? Special attention must be paid to proper ground plane and connection to the antenna. The antenna should not be placed inside a metal cabinet, and even a plastic cabinet can de-tune the antenna. Secondly, consider the power supply for the module. The power supply for the module must be designed to provide full power without voltage drop during the RF transmission peaks. This caution applies especially for the High Power modules which will require > 500mA peak during transmission. The transmitted RF signal will be distorted and not possible to receive if the supply voltage is unstable during transmission. When testing with battery driven demo boards, it is important to assure that the batteries in use are fresh and able to deliver sufficient peak power without dropping the voltage. Thirdly, the range can be increased by switching from the non-HP variant to the HP variant (if local regulations allow this). Finally, using lower data rate, or switch to t a narrowband module will improve the sensitivity and hence the range as well.
Last Update: August 8, 2017