The "iBlast" network, announced Tuesday, will broadcast over a portion of the digital spectrum that the government has allocated to local TV stations to provide high-definition television.

iBlast expects to begin providing service in 102 markets early next year, broadcasting through 143 local stations affiliated with the network's backers, which include Tribune Co., Gannett Co., Cox Communications Inc. and New York Times Co.

The affiliates, some of which serve the same market, would continue to provide their own mix of TV programming in addition to the new content from iBlast.

Because digital TV signals require less capacity than traditional broadcasts, the new spectrum allocated to each station for digital TV has enough room to carry more than one program at a time or additional content such as iBlast's proposed downloads from the Web.

However, since a broadcast signal needs to be scheduled for specific times, downloads won't be available "on-demand" like they are with other Internet connections. Another limitation is that a broadcast connection doesn't allow two-way communications like a dial-up connection, a high-speed cable modem or the telephone-based service called DSL, or digital subscriber line.

Still, since more than 60 percent of all U.S. households can now receive a high-definition, digital signal from one or more TV station, broadcast delivery has an early jump-start on the competition.

iBlast President Ken Solomon said TV broadcasting offers a more immediate way to bring high-speed Internet access to people who can't afford more than a dial-up service or those who live in areas where the cable systems and telephone networks haven't been upgraded yet for digital communications.

"Two-way cable costs $40-to-$50 a month. That's not for the masses," Solomon said.

Using iBlast, a person who goes online with a regular dial-up telephone service can buy a music album and then receive it with a special antenna attached to the computer, downloading at far greater speeds than the dial-up connection can provide.

iBlast said its broadcasts can deliver data up to 200 times faster than a conventional dial-up modem, and five times faster than a cable modem or the telephone-based service called DSL, or digial subscriber line.

Still, because broadcast doesn't have two-way capabilities, iBlast is trying to position itself as a complement to other Internet services.

The federal government has ordered all TV stations to switch from today's analog signal to digital by 2006. During the transition, stations are airing programs on two channels— one in digital and the other in analog — so people can still watch broadcast shows on their analog TV sets.

The other partners in the iBlast venture are Post-Newsweek Stations, E.W. Scripps Co., Meredith Corp., Media General, Lee Enterprises, McGraw Hill, Smith Broadcasting, and Northwest.