Over the air antennas indoors sometimes work great. Especially if you live in town close to where the local TV transmitters are located.
But if some stations are pixilated and are fading in and out, that is a sure sign of a weaker signal. That a small indoor antenna may be struggling with.
One easy way to fix this (without climbing on your roof) is to install a larger antenna in your attic. Usually, you have a lot more space to place a larger antenna in an attic. And be sure to hang it up as high as possible from the rafters.
Larger antennas do a much better job of pulling in distant channels. Size does matter when it comes to antennas, as does how high it's placed.
A good antenna to check out that works well in attics is the omnidirectional Antop UFO Antenna. Unlike some antennas, this UFO antenna also looks pretty cool hanging on a mast on the roof.
So if a small indoor antenna is not cutting it. A larger attic antenna can receive those free distant HD over the air TV channels.