Use a high quality Diplexer. If you are a contractor or retailer there is a list of approved equipment to be used in Dish installs. I use Holland STVC exclusively @ $1.00 ea and Holland DPD2 @ $2.00 ea if and only if I am using a DPP 44 Switch.
This is CABL.com posting #180816. Tiny Link: cabl.co/mVcy