Sinclair Broadcast Group and Nexstar Media Group said today that they will share airwave spectrum in 43 markets where they both have stations to promote a transition to a new broadcast standard — ATSC 3.0 — that supporters say could revolutionize over-the-air TV.

The new standard will make it easier to meld 4K programming and interactive broadband data in over-the-air transmissions. But it will not work on current TV sets.

As a result, companies expect the FCC will allow channel sharing so stations can  simultaneously broadcast their programming in the current and new standards.

The announcement comes as broadcast, cable, and tech companies lobby the FCC to be sure that they and their customers are protected during the transition. For example. cable groups want regulators to require broadcasters to continue providing programming in the current standard.

Early this month a Sinclair-based organization promoting ATSC 3.0 told the FCC that “simulcasting will not always be practical or even possible.” Stations that can’t do so, it added, “should nonetheless be permitted to upgrade their service.”

In a letter to the FCC today, the American Cable Association said that’s “an unacceptable response to potential service losses caused by a broadcaster’s voluntary transition to a new transmission standard” that also could “open up new revenue streams unrelated to broadcasting.”

Nexstar and Sinclair reach about 60% of U.S. households. They forged an alliance in March to promote ATSC 3.0

They say that the transition has been “complicated” by the FCC’s recent spectrum auction. Stations agreed to let the government sell some of the airwaves they had used to wireless broadband providers.

That why coordination between competing stations is “critical to ensuring that a transition to the upgraded technology can occur,” they say.

Sinclair and Nexstar plan to make the switch in 97 markets, including 54 where they don’t compete. They’ll disclose specific plans late this year, they say.

Sinclair CEO Chris Ripley says the companies are “confident that through our coordination and mutual efforts we can navigate this transition together”

Nexstar CEO Perry Sook says the changes “will enable us to remain highly competitive in today’s multi-platform environment.”