Range Problem of XBee Pro S1

[Ming Hao]

Hi, I have buy 2 XBee Pro S1 from
https://www.sparkfun.com/products/retired/8742
for doing my fyp but I meet the problem about I am not able to get more than 100m in line of sight when I doing range test at housing area.The setting of two XBee is all default setting.
if there is any tuning need to be done?

Besides that, can my Xbee Pro S1 add on extra Antenna gain?