I'm assuming that the 505 can tune HD channels. If so, yes, it will send those channels out the RF-coax port, however, the images will be SD quality. See the following FAQ:
RF-coax is the "worst" picture/sound quality source and you should use anything else unless you don't care about picture and sound quality.
If you want HD, you'll need either HDMI or Component video. Or you can run cable(s) from your dish and use another receiver for the TV in question.