OTA question regarding HD locals I already recieve

I already reiceiev several of my networks, but for example on NBC the PQ sucks, so unless I have to record it, when watching it live I watch it through my TV tuner, if I set up the OTA on the HR20, will I still be able to get both the DTV HD signal for my local NBC and the OTA signal and if so how will it work since they are both channel 5 or will the HR20 default and only let me get the HD channel 5 from DTV assuming that is the better signal (which normally it probably would be but in this case this is one that ahs that annoying 8mm effect). Thanks