Dish not aimed will give this problem, switch not hooked up correctly will give this problem, using the wrong lnbf versuses coax hook up will also give this effect, using damaged or incorrect coax will give this effect, contaminated connections will give this effect, splitters in line from the dish to the receiver will give this effect, not knowing what your doing will lead to all of these giving this effect.
What we need from you is details to the installation, how is the dish mounted, is the line of site to the south south west clear, are you using rg-6 coax, are you using twist on fittings or compression fittings, are there any splitters in the lines, what lnbf / switch configuration are you using, ect ect ect.