need to know more, what kind of antenna is it?
a directional antenna can be pointed toward the transmitter, omnidirectinals won't make any difference.
how old/long has it been there? was it always like that? coax could have a bad connection somewhere, feed point, or chewed through by a rodent, that is the first thing to check is the coax...
if it is amplified, try unplugging the amp. I've had more than a few amplified tv antenna's that the amp went bad and actually ruined the signal with interference when plugged in.
also you may have already noticed, but within the last month or so, many channels in many areas changed transmit frequencies, and everyone should have done a re-scan on their tv tuners. the new frequencies may not be picked up as well with your current antenna location. the FCC and TV stations did a HORRIBLE job communicating this, I hear people every week complaining they "lost" channel so and so...a rescan fixes it and possibly rotating the antenna as well.