When you use RF over coax, the receiving device must have an analog tv tuner to pick it up. Your projector doesn't have an analog tv tuner. Plus as the previous poster said, even if it worked, it wouldn't be HD and will look absolutely terrible.
If you really want to go through with this plan, just pick up an old VCR, connect the coax into it, tune it to the channel that has the signal from the 722 (probably 60 something), then connect composite out from that into your projector.
Since that's a nice HD projector, I highly recommend you try to send it an HD signal. There are a couple of ways to do this. That white connector with all the holes is DVI. You can get a cable that's HDMI on one end and DVI on the other. That will get HD video to it, as will the component video output. Use the red/white audio outputs for sound. If you can't run any cables, a wireless HDMI system like the Actiontec MyWirelessTV is a good option. I have one that works very well about 30 ft through a couple of walls and a floor.