Thanks everyone. I looked for the various things you guys indicated and didn't have any luck. I did, however, notice two screws, with two wingnuts, towards the center. I figured what the heck--went to Fry's, bought a 300 to 75 outdoor transformer, attached the twin leads to the two screws, tightened the wingnuts, ran the line, and HOLY CRAP MY RECEPTION IS AWESOME. I guess all that matters is that it worked! And everything is at least at 90%--I'm even receiving a channel that broadcasts from about 100 miles north of here.
Also, just for trivia--my attic is not metallic, but rather covered with that heat-reflective stuff they put on tanks, heh. It gets hot here in Phoenix in the summer and that stuff probably cut $40-50 off my summer cooling bills. I was afraid it might interfere with the antenna but obviously it's not causing too much trouble!
Again, thank you everyone for your ideas!