This very topic is quite interesting. I've had poor experience with this which is why I pretty much give up using the antenna and resort to DVD movies we bring from home. You might have read a few of my posts mentioning I wished I never had the roof antenna mounted, just as I had the factory do with my roof rack and ladder.
At home in the house, we have a digital converter that came in handy to point our roof-top antenna toward the source. There is a feature to identify signal strength, so with Walkie-Talkies, my wife instructed me to turn the roof antenna until the signal bar was at it's best.
In our 2007 PC with aftermarket 26" Samsung TV, that signal strength feature might be built into the TV, but I could not find it. With digital technology, you have to pre-point the antenna to the right place, cross your fingers, scan for channels, and hope for the best. In the places we typically camp, that process almost always yields nothing. If I get two stations, I am doing great. But they are weak so then what happens? Digital pixelation and the sound cuts in and out. So out comes our DVD binder with all our movies.
The analog days were real simple and reliable. Turn on the TV to a popular station like channel 2, 5, 7, and then turn the antenna until the picture is at it's best. It was a very forgiving process.
One final nail in the digital coffin is that digital technology requires line-of-sight. If there is anything between you and the signal source, like a grove of trees, it's Tough-Luck-Charlie. Supposedly you should be able to get a signal bounced off a mountain or canyon wall, but never any good luck there for me.
The only time the antenna actually works well is when we are staying in a larger city that broadcasts a digital signal. But that places us into RV parks. And guess what RV parks have......Cable TV offering many more channels...clean signal channels. So what good is the antenna?
Okay I will type this again. I sure wished I had PC-USA give me the Winegard antenna in it's shipping carton and free my roof of more holes and unsightly caulk, especially because it it mounted up front in the nice B+ cap. It would also eliminate the nasty rattling the antenna makes when the roads are a bit rough.