On your feedhorn (where the LNB is) there is probably a blue box with a motor inside. This controls the polarity and skew which will fine tune your signal.
Without it you will not get a good picture, like you are getting.
From the back of the receiver there will be a 5V, pulse and ground which controls the motor. Red is 5v, Black is Ground and White is pulse or a symbol that looks kind of like this _-_
Whichever 3 wires are connected at the back of the receiver should be connected to the 3 at the little blue motor.
Then if the picture is still not clear, you can go into the menu of the 920 and adjust the skew to bring it in better.
If you can not find out which wires go from the actuator you may have to un-tape them to have a look. The fewer wires the better! Having more than you need will only confuse things.
Once you get a good signal on the analog channels (like C-Span) then you will be able to get a proper digital signal to get the other channels you speak of.
Good luck
