Radio waves have their limitations (remember, TV signals are radio waves). Just like the headlights on your car lose their brightness farther and farther down the road, TV signals lose their strength the farther they travel from the transmitter. Atmospheric conditions and interference from other TV or radio frequencies can weaken these signals even more. The result is static, or ghosts, or other poor reception.
Digital TV uses the same radio waves, yet DTV overcomes these obstacles and delivers a crystal clear picture and sound.
This is because the digital information being sent to your DTV set contains more than the information needed for pictures or sounds. The signal also contains special "proofreading" code.
As a DTV set receives the information to draw the action star crashing through the sugar glass window, it compares that information to the proofreading code. If there are errors or imperfections (say, some ones and zeroes weren't received to create the picture), there's enough information in the proofreading code for the TV to do a quick mathematical calculation and put ones or zeroes where they belong. It's doing these calculations thousands of times every second.
What you see is the "edited" work, a perfect picture.
But it's all-or-nothing with digital TV.
As long as your TV receives enough ones and zeroes to interpret the picture or perform the code checking, you get the perfect picture DTV promises. If the amount of interference exceeds the amount of information, you don't get a fuzzy, static-filled picture. You won't see the channel at all.
We can compare this to Morse code. You either receive enough dots and dashes to piece together the message or you don't.