I've been trying to adjust my ExpressVu satellite by aiming it differently this weekend. I only have SD tv and am looking for Nimiq 91W. I get a signal of 90 to 100% on most but not all transponders. Specifically, transponders 8, 10, 24 are not working at all. I think my receiver is a 3900 and the dish is an old round model - not sure the exact size but it may be 20". Can anyone help me to figure out why I can't get some of the transponders?