The best way to do this is to configure the radios in a classic point to multi-point configuration, then send your data.
Base:
DH 0x00
DL 0xFFFF
Remote (s)
DL = SL of base
DH = SH of base
Test this by sending data back and forth and moving nodes till they are out of range. Than move back till it is in range and add one as a router at that location. Then keep going farther out.