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Dave is correct about the IF freq, but: the local osc in the LNB
covers two ranges: 13 to 18 VDC it will osc in the low band, 22-28 it
will osc in the high band. The LNBs I've seen use an signal about
20khz sent from the satellite reciever to switch polarizations.
Adjacent channels are oppisitely polarized, circularly.

The normal DTV uses 13 or 18 to switch polarity. The 20kHz is
probably required for the triple or dual LNBs to select which
of the three birds is being received.

Pete