CMU has cable.
Unless you find an apartment off campus, you're going to have a hell of a time receiving anything at all on CMU's campus. I know a guy over there who gets HD on a modded dual double bowtie Radioshack antenna. He gets CBS and NBC and I believe he has a north-facing window. Don't even try omnidirecitonal, Oakland's buildings and terrain will make it impossible for you to get anything.
If you're high up, you have a much better chance. You will probably only be able to get stuff in the direction your window faces. If you are facing north or west, you'll be able to get CBS, NBC, and probably PBS. If you face south, you MIGHT be able to get ABC (good weather, high floor, and clear line of sight generally required for good reception), and if you face east, say goodbye to HDTV. On the upside, you can pick up MTV 2 for free on analog OTA (I believe it's channel 29)...
I doubt we'll be seeing any HD over campus cable systems anytime soon. Yes, CMU and Pitt have Comcast cable, but it's not normal comcast cable. It's like Pitt has its own facilities serving the dorms, as last I checked, digital cable and many premiums were not available, and many of the channels are actually different. Your best bet is to get an off-campus apartment and hope Comcast comes through with HD sometime this century. But I know that CMU requires all of its freshmen to stay on campus, so you'll be waiting at least a year.
One thing you could try if you really lose your mind is plugging your RF input on your capture card into the building's groundwork, thus using it as a huge multidirectional antenna. DO THIS AT YOUR OWN RISK. YOU COULD FRY YOUR GEAR AND YOURSELF. I tried it once in Tower B at Pitt and I actually got some very good analog reception, but the ghosting caused by all of the interference was too much for me to lock a digital signal.
Welcome to the incessantly frustrating world of HDTV in college. Between living in an urban area, not owning your property, moving every few months, and always being broke, you'll find that this definitely is NOT the hobby for college students. Luckily, I'm finally moving into a house with a good landlord on South Bouquet and we're going to put up a big rooftop antenna. This is after two years of struggling to get anything in campus housing... free at last!
"There's a... big machine in the sky... Some sort of... electric snake. It's headed right for us..."
"Not yet. I want to study its habits."