Hi Sergey,
I guess that you transmission power was setup on TXmin, otherwise this does not have any sense. I have manage with same configuration and maximum power to go over 660m. With TXmax and with configuration of preamble=1024, PRF=64 and DWT_BR=110K i still manage to go around 600m in outdoor (for channel 2), obstacle free, flat hill environment. 30m distance i have only with minimum transmission power.
Cheers
Nikola