RF above several MHz travels on the skin of the conductors and generally does not penetrate to the steel core. Directv and Dish Network call out solid copper center conductors only for low DC resistance when powering LNBs, multi-switches, etc. The lower DC voltage drop using solid copper center conductor will allow a slightly farther coax run for these systems but there is no performance benefit otherwise.
This is CABL.com posting #250121. Tiny Link: cabl.co/mbden