Using my D12MP-500 box in my RV

Yes. However, DIRECTV is shutting down all MPEG2/SD feeds so soon your D12 will become useless. Also, if that RV dish you are referring to only receives satellite 101, it too will become useless. Going forward, you need an H24 or H25 receiver for camping (or HR24 if you want an HDDVR) as well as a SWM SL3 Slimline dish. These dishes can be mounted on a sled mount (non-penetrating mount) or on a tripod. Additionally, there is the Winegard Trav’ler (little expensive) which automatically finds the satellites by itself and doesn’t require you to aim the dish.

What are your current SIX receiver models in the house? Receivers starting with ‘D’ or ‘R’ (with the exception of an R22) must be replaced going forward. This replacement is known as an ‘SD SWAP’ and is done FREE BY DIRECTV. You shouldn’t need a technician to come out and install the parts since you already have a Genie and that likely means you have a SWM system already.

@scottsdaleRVer 

Simple answer is not anymore.

DirecTV is shutting down their MPEG-2/SD-only feeds. Though the D12 works on SWM like the Genie, but cannot view Whole Home DVR, it is the last MPEG-2 receiver made. It will soon be a brick.

You would need a H or HR model if you wanted DVR in the RV. With the box you would require either a slimline SWM dish on a tripod/sled mount or the Winegard Trav'ler.

If you have an R22, that would also work. Though model number says SDDVR, it is MPEG-4 capable (hence HDMI port). Was for areas that long ago adopted MPEG-4 locals, but were still using SD-only service. Think of it as an HR22 in hiding.

Does your box actually have "MP" in the model number? Just curious as that seems odd.

Call DirecTV and request a MPEG swap of the D12. Do NOT say "upgrade". Verify it is for a non-DVR reciever (such as H24 or H25) to be the equivilent. Do not accept a Mini Genie Client as that cannot work without the main box, so will not go by itself in the RV. Plus the Genie can only support up to 3 Clients at the same time anyway.