I think what pe1chl tried to explain is that you've to tweak to the minimum, because that's where the 'polarization discrimination notch' is maximal.
In other words: listening to a H-beacon (or program), switch the LNB to V and tweak for minimum signal.
Many broadcast satellites have two (different) programs on the same frequencies/transponder but with different polarities (H and V).
Assuming around 25 - 30 dB polarization discrimination for linear polarizations it's possible to obtain clear (DVB-S) pictures with C/N's of around the same magnitude.