More than a half-century ago, the federal government took a big step toward the media business when President Lyndon Johnson signed the Public Broadcasting Act into law.

Because of that bill, PBS, NPR and other public broadcasters in the United States receive more than $500 million annually from the government-funded Corporation for Public Broadcasting.

That support is now hanging in the balance. The Senate is planning to vote this week on a proposal to strip the funding for the Corporation for Public Broadcasting, a move that could be catastrophic for radio and TV stations across the country.

Here’s what you need to know.

Would NPR and PBS survive?

Yes. NPR gets about 2 percent of its annual budget directly from federal grants, including from the Corporation for Public Broadcasting; for PBS, that amount is about 15 percent. Both organizations also get federal money indirectly, through payments from member stations across the country that receive government funding, though it’s difficult to estimate precisely how much.

The real pain will be felt by local stations in far-flung locations like Unalakleet, Alaska, and Pendleton, Ore. Those broadcasters often rely disproportionately on federal grants for their operations because of a funding formula that takes into account the fact that they have fewer donors and programming sponsors.

What about local stations?

An internal NPR report from 2011 obtained by The New York Times said that if Congress cut off funding to the public radio system, up to 18 percent of the roughly 1,000 member stations would close, with broadcasters in the Midwest, South and the West affected the most. Nationwide, up to 30 percent of listeners would lose access to NPR programming.