Where are modules placed; indoor or outdoor?
For indoor, 112m is module's range as per manual.
For outdoor, this is quite less. Look out if there are any obstacles in Fresnel zone. There are few articles on it, which might be helpful for you:
http://www.digi.com/support/kbase/kbaseresultdetl?id=2090
http://www.digi.com/support/kbase/kbaseresultdetl?id=2051