I know you have
sg2100, but check out page 18 of
http://www.sadoun.com/Sat/Products/S...OUN-SM3D12.pdf manual. It gives some general ideas what to do if you are not tracking your arc.
I also have sg2100 and I can track from 30W to 129W with pretty good signal on both ends of the arc. I think my pole is not perfectly plumb, but it is good enough to cover the whole arc so I don't want to mess with it.