The HR24 receiver can display SD only, HD only or both but for HD you must have a HD capable dish. You can use the 2 turner multiswitch inputs or just one with a SWM dish.
The HR44 can display can display SD only, HD only or both but you must have a SWM dish.
The 18" round dish is SD only. For HD you need a Slimline equivalent dish that is either multiswitch capable or SWM.
OP Your mileage may differ depending upon what type of dish and receiver you have at home.
I had the 4 coax Slimline at home with a multiswitch and 2 coax to the HR24. Moved the HR24 to the rig with a 18" dish and 2 LBNs and configured the HR24 for that dish.
I now have a Slimline SWM dish at home and a RF Mogul SWM dish on the rig. The HR44 works on both with no configuration changes. It's also uses RF for the remote and as such is behind closed cabinet doors.