DP plus LNB's don't switch between H and V transponders, they use band-stacking to get both transponder polarity's down the coax at the same time, this is why in the LNB setting OSC-DP must be used, this sets up the receiver to use two LO frequency's, one for the lower band and the other for the second band.

The coax used for this type of LNB also needs to be rated to a higher frequency then a legacy LNB, it must go to at least 2.5 GHz or be swept to 3 GHz, or you will be missing out on some transponders.

Most FTA receivers will work OK at a signal level around 60% S, all this "S" reading is, is the level of the signal from the LNB it's self, not the signal from the satellite, that would be the "Q" signal, the "Q" should be as high as you can get it by tweaking the dish.

If the "S" signal is below 50% then there could be a problem with the coax, coax connector, a switch (if used) or the LNB it's self.

With a DP+ dual satellite LNB there should be no switches in line with the LNB or receiver, this would cause problems as the DP+ dual satellite LNB has it's own internal Diseqc switching.

Diseqc port 1 would put you one one satellite, Diseqc port 2 would put you on the second satellite.