The Zenith system uses Single SIde Band transmission which achives the farthest distance for the lowest power. Multiple video/audio streams from 1080i60 down to 480i60 are compressed via MPEG-2. This extended range is achived by occupying the entire 6mhz bandwidth 100% of the time. That is unused bandwidth is always filled in. Error correction is applied and a randomizer turns the digital data into 6mhz of white noise. The end result is an amazing ~19mbit/sec data transfer rate in a 6MHZ channel and a signal reach comparable to the original 480i60 analog and beyond any other digital transmission method. Current 6th generation receivers have leveraged DSP technology to greatly improve reception of 8VSB terrestrial ATSC signals, achieving communication grade receiver results. Improvements to the original ATSC 8VSB standard allow software to now cope with multipath stituations and make Urban ATSC reception possible.

DVB COFDM digital modulation
ENTER DVB (aka COFDM): OFDM was developed for the U.S.military in the '60s, along with TDMA (aka GSM) and CDMA, etc. COFDM was further developed by the French throughout the '80-90's, but was not practical and low cost enough until recently (after TI introduced the DSP processor). COFDM uses advanced DSP to generate ~1000 or so carriers spaced a few KHZ apart (esentially like having a thousand 9600 kbaud modems operating together. COFDM is better able to handle multipath since its data streams are very slow, but is more susceptable to wide impluse noise (ie. electrical noise), and also requires much more power than 8VSB just to achieve a smaller coverage area.

DVB in Europe started widescreen EDTV digital terrestrial transmissions (8MHZ wide) back in 1998, the same time the U.S started its widescreen HDTV digital 8VSB. However, controversy over 8VSB vs DVB and the available receivers/TVs of the day prevented consumers from buying ATSC equipment until the FCC finally setteled the arguments in 2002. Currently almost the entire U.S. has ATSC coverage and almost all current TV programs are HDTV

Europe has started HDTV transmissions as of 2006.
The U.S.A. has ended analog transmissions as of June 12th, 2009

LCD & PLASMA DISPLAY TECHNOLOGY
As of 2012 the CRT and Plasma screens are now completely obsolete. LED displays are incorrect. They are not LED displays, but backlit by LED's. Some day in the future a true LED TV will emerge.

Progressive Scan
With todays LCD/PLASMA screens, the issue of interlaced vs progressive scan comes down to the original recording itself. . When video is recorded in interlaced format, you may get motion defects, progressive displays take the 2 half resolution fields and stich them together using a computer algorithm to prevent those motion defects. Hopefully, In a few years HD cameras will shift to 1080p60, so 1080i60 ATSC will display as 1080p30 without defects. The latest displays can now display 1080p60, but the ATSC format does not allow for 1080p60 due to the massive bandwidth required. Only the new HD DVD players can send 1080p60 and only over HDMI.

HDMI (aka DVI with audio)
HDMI is a triple low voltage differential digital data stream carrying video and audio. HDMI sends pixel data in an RGB or YCbCr format. HDMI is ATSC,DVB,VGA,DVI compatable. This makes the HDMI the connecter that works almost anywhere in the world. The hardware was a modification of the original DVI system. HDMI and DVI were designed in the U.S.

FCC
The FCC has in place a rule that any person who wishes to receive TV over a small dish or OTA TV antenna has that right and that no other law can prevent that. Rule 47 CFR Section 1.4000 has been in effect since 1996. You are limited to a height of 12' above your roofline. There can be restrictions, but they must be reasonable.