Verified answer

It has to do with the signals being used. The antenna still needs a tuner, which is why it uses coax.

Things like your DVD player, cable/satellite box, or game console use a different signal format, and don't use a tuner.

No antenna, HD or otherwise, comes with a HDMI hook up.

The antenna has to be hooked up to a HD (ATSC) TV tuner which is either built into the TV or as an external tuner. The tuner tunes in one station and then sends that one HD video & audio feed to the monitor or TV. If it's an extrernal tuner, it would be sent through a HDMI cable.

If you are using a TV with a built in ATSC tuner, there is no HDMI cable to be seen. The coax transmits all of the analog & digital signals to the TV and the internal ATSC tuner picks one to decode.

HDMI cable serve the same function as composite or component cables do with an analog TV.

Additional:

>Also do HD tvs come with a coax hook up?

Yes, HDTVs have coax hookups. "HD Ready" TVs will only have a coax input if they have an analog tuner built in.

HD antennas are an RF input, while the HDMI connection is a Video input to connect DVD player or Cable / Satellite boxes.

They're different TYPES of connections, just like the COMPONENT connector is....Component inputs are also Hi Def.

Your HD antenna can recieve the LOCAL channels, but the HDMI will connect you to the cable or satellite boxes that can recieve all the Network-based stations like TNT and Discovery and TLC and QVC.....