Some LNBs need a VERY clean powersupply.
In case that most of the LNBs have internal voltage regulators at 6 volts (like 78L06) , one can power the LNBs with voltages down to 8 volts. (which also keeps them nice cool)
So it's possible to use 12 volts from the rig and filter it in an additional voltage regulator to 8 / 9 volts for example 7808 or 7809
This gives a very clean LNB supply.
And don't forget the capacitors at the regulator.