If you wish to use MRV, and why wouldn't you if you have DVR and multiple other TV's, then NO you can't not combine OTA with your DirecTV signals, as the MRV uses OTA frequencies to stream content to your other TV's. If you wish to have a OTA connection to each TV as well as the DirecTV feed then you will have to install a separate cable for the OTA. If you want to use an AM21 or AM21N OTA tuner module it can only be used with DirecTV DVR's. If you record an OTA Channel on the DVR with the AM21 connected then you can stream that recording to the other TV's if you have MRV.
John
John