If the TV is digital, you won't get a snowy picture and scratchy sound like with an analog TV - it's all or nothing.
You don't say how far you are from the nearest broqadcast tower, but if you're more than 30 miles you might find a "Wingman" helps your reception.
I get much better reception using www.antennapoint.com
and my iPhone compass. The "Wingman", whether it works or not, is a good direction pointer to use for aiming at the nearest broadcast power.