The National Association of Broadcasters (NAB) is giving the viewing public a heads-up: Your local channels are probably going to be moving soon.

Here’s the reason: Earlier this year, the FCC held an incentive auction in which local TV stations sold the rights to their airwaves to wireless providers in exchange for new spots on the dial. The auction, which raised billions of dollars for local television markets, allowed T-Mobile in particular to expand its wireless network significantly.

But with the sale of the spectrum comes a rocky change for broadcasters: Many are likely to move around the dial over the next few years in what promises to be the biggest shake-up for local television since 2009’s digital TV transition.

With that in mind, NAB is implementing a plan to make the shift less painful, including the launch of TVAnswers.org. In English and Spanish, the website explains what viewers can expect in the coming months and how local markets—encompassing nearly 1,000 television stations nationwide—will be affected.

The association, which also managed the 2009 transition, is planning to help customers “rescan” their television sets to pick up the new channels. The changeover, which will take place in 10 phases between 2018 and July 3, 2020, will affect a not-insignificant 77 million people who tune into over-the-air TV.  Cable or satellite subscribers will not be affected.

“NAB is devoted to working with Congress, the FCC, the wireless industry, and third-party groups to keep the public informed throughout this enormously challenging undertaking,” NAB President and CEO Gordon Smith said in a news release. “Broadcast TV remains Americans’ top source for local news, weather, community programming, and emergency information. The broadcast industry is committed to ensuring no viewer is left without these services.”

NAB is also working to roll out tools for local television stations around the country to help them communicate with viewers about the changes.

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