The amplified "digital TV" antenna I bought last year has never performed very well in our house; the signal level varies a lot, and is often so low that the station is lost for minutes at a time. I tried an experiment quite a while back, and ran a cable up to the roof; I stood up there pointing the antenna around to see if altitude and a really clear line of sight helped any. The results weren't encouraging.
I finally decided to do something about the situation (e.g. basically unwatchable TV) when I came across this article from Make on an easy-to-build antenna design. I had most of the parts already lying around the garage, and a quick trip to OSH got me the rest for about $5.
Testing in the house showed that the home-brew antenna performed just about as well as the amplified antenna -- but that still wasn't what I was hoping for. Today, I took the new antenna up on the roof, and the results were very good. Channels that used to be at signal strengths of 5-6 are now pegged at 10, and the fluctuation I used to see is gone. Success!
My next step might be to cannibalize the old antenna to steal its amplifier...