i think pretty much all HDTVs nowadays have built in hd tuner, aka. hd receiver in their tvs and its called ATSC. ATSC is to replaced NTSC analog tuner so we can watch digital broadcast on our hdtv and even sdtv...
I think its different than DVB-T broadcast which I think its mostly use in Europe... Either way, you just connect the antenna that you use for the analog sdtv to the hdtv RF input....if it\'s digital RF input and let it scan all the digital channels that it can receive with the antennae. and presto, you can watch broadcast digitally. And some shows are broadcast in 720p and 1080i too.
So, basically, just aim at the antenna where the signal is the strongest to receive digital over the air broadcast like from a tower that is the closest to where you live, so you won\'t get hiccups and picture breaks up from weak signal. Think of it like how if you have a good dvd disc, you can watch it without screen freezing or breaking up. but if the disc is dirty or scratch so badly, it couldn\'t read it well enough and you get break-ups and screen freezes...
you don\'t need a fancy antenna for that, any antenna for tv should work for receiving either analog or digital tv broadcast. But if you have an antenna that is hook up on the roof, is better.
If you are one of those early adopters that own an hdtv that doesn\'t have built in hd tuner, you can buy an external hd tuner, or hd tuner with HDD to record digital broadcast or hd tuner with dvd recorder...or 3 of them...
But if over the air broadcast is not your thing, you can get directTV with digital broadcast with a lot more channels selection. But it requries DirectTV external set-top-box...or digital cable...be warned as they have more compression than regular digital over-the-air broadcast...
Also, last but not least...some hdtv also have cablecard built on the tv, usually on the back of the tv so you don\'t need an external directtv box or cable box to watch digital cable. All you need is just a card and that\'s it. Save space on box, and no need to connect all those wires like video/audio cable, and no need to plug in another A/C power. more convenient...