Dish uses two sets of three satellites, with duplicate programming on both sets for the most part. Some locals are only on one set or the other, while other locals are only on one set in HD and the other in SD. The "Eastern arc" sats are located more towards the southeast on the orbital arc not surprisingly, with the "Western arc" sats more towards the southwest. The eastern arc sats are at a higher elevation as you near the east coast, and the western arc is higher to the west. Both sets of sats are viewable everywhere in the lower 48, although the western arc's lowest sat at 129 degrees is very difficult to "see" from the far northeast due to its low elevation and fringe footprint. Since the two sat sets are at different elevations and in different directions from any location, when there are obstacles like trees, etc, one set is often easier to "see" than the other, making a dish that's capable of using either arc a definite advantage. Because the spacing of the sats is different for each arc, different LNBF's are needed for open face dishes, and switching LNBF's on an open face dish like the 1000.2 only takes a few minutes. Only a few automatic dome dishes are capable of dialing in both arcs, but your Carryout 1518 is not one of them. The 1518 only can only use the western arc satellites.
