Conjuror said:
Just to crash a myth. When you receive a digital signal, you receive a stream of zeros and ones. If the stream is never broken, you'll always get perfect picture, no matter how far TV towers are. If the stream is broken sporadically, you cannot get the picture at all or you have a lot of droppings. An amplifier CANNOT boost broken digital signal.
Good: picture is always the best possible if you can get the signal.
Bad: If the signal is really weak, you cannot get even a "snowy" picture as you can get with analog signal.
It is simple, isn't it?
Conjuror....
You have a basic understanding of how it works, but are making a critical mistake. There is no such thing as a digital transmission. Everything, and I mean everthing, that travels over the airwaves is analog. Digital information is encoded in the transmission by modifying the analog radio waves.
If the radio transmission is too weak to decode the digital information embedded in it, then like you mentioned, you get no picture. And, if enough info is there, you get perfect picture. However, you most certainly can boost or amplifiy the radio transmission, so that is is strong enough to be able to properly decode the digital information embedded in it.
If it helps, think of it the way a modem connects over the internet. Computers speak to each other in Digital. But phone lines are only designed to carry analog information. You need a modem to convert the bits to analog for transmission over the phone line. At the other end, the analog information is then demodulated back to digital.
It is much the same with OTA digital channels, except the transmission medium is RF radio instead of a copper wire.
[Technical folks.. yes, I know, it's not exactly the same, but it serves to illustrate the concept]