A PLL LNB is much more stable in frequency than a DRO LNB. For high data rate traffic, a DRO LNB is sufficient. This is because the bandwidth of a high data rate carrier is large, so the frequency tolerance of the LNB is not so important. However, for a low data rate signal occupying a narrow bandwidth, the stability of the oscillator within the LNB is more important. For a 500KB/S link, a PLL LNB will be required.