I've had the exact same problem off and on for 2 weeks now. Transponder 18 on Anik-F3 is very weak compared to the rest from our view of the sky.
When Dish was testing to prepare for Ciel-2, a new spotbeam was listed on one of the uplink reports for St. Louis HD locals. Maybe they will turn that on sometime soon. I'm thinking it is part of their Western Arc plans. Does anybody know for certain?
-OD