Well first of all, WHICH kind of HR20 is it - an HR20-100 or HR20-700; this DOES make a difference...
If it's an HR20-700 - NO "adapters" are needed at all; however, you WILL need a DECA unit if you have MRV &/or Cinema Connection thru the coax. (just like any other HR2x DVR OUTSIDE of the HR24's)
If it's an HR20-100 - depends on what you're doing with it:
- if you are JUST putting it on an SWM system & do NOT need a DECA unit on it (NO MRV or Cinema Connection used thru the coax) then you do NOT need any adapters; just connect the (single) coax to the SAT 1 input on the receiver, just like any other HR2x model.
- if you are putting a DECA on it f/MRV &/or CC) then you have to use this hookup) as follows: