Why is the reception of my DTV sucky in some channels?

No, it means that the signal is weak for those channels. Digital television is very different from og. With og, when you had a weak signal you would receive a "fuzzy" picture, with digital and a weak signal, you receive no picture. If you want to improve the digital channel quality you need to mount your antennae as high as possible, your roof is the best place since you can get a signal with the least amount of obstacles.