Having an issue with signal strength on transponder 129. Signal varies from 10-15 and drops out frequently. Transponder 110 is steady at 75--solid. Transponder 119 is steady at 50--solid. Dish 500 with a triple LNB--(don't have a model). This setup is in northwest indiana about 40 miles southeast of Chicago. There may be a tree issue but I don't understand how 110 and 119 are so strong and 129 is marginal. Hints? I can provide additional info if needed. Thanks