Got it! Darned landlords.
Do you have any amplifier on the antenna? Might be worth that $20-$30 to try a high quality amp between the antenna and your receiver, and then just return it if there isn't an improvement. With the switchover to digital transmission, things should be much less spotty/variable than in the prior analog world. If it works at all, it should work perfectly, all the way down to a very steep dropoff where the signal is not strong enough for the error-correcting to be effective, and it fails completely.