External antenna not supporting long distance

I am using XBee Pro 63mW RPSMA - Series 2C (ZigBee Mesh). Tested with external antenna but it not supported the distance long range. Approximately working distance is 65 meter. Tx power level is highest[4]. It is possible to increase distance up to 1.5km covering range/not ? Please guide me to solve this issue.

Duracontrolsystems,

This is something that you really need to contact Digi Support over by sending an email to tech.support@digi.com

Digi Support