Broadcasters and free-speech advocates say they will appeal a new Federal Communications Commission rule banning sexually explicit programming from the airwaves.

The agency issued the rule Wednesday in response to a new law that closes the FCC's current midnight-to-6 a.m. window during which indecent material may be aired."Our view is that the statute is plainly unconstitutional," said Washington, D.C., attorney Timothy Dyk, who is representing a coalition of broadcasters and free-speech groups.

One FCC commissioner, Patricia Diaz Dennis, also said she has constitutional questions about the rule because recent court decisions have upheld First Amendment protection of indecent broadcast programming.

The Democratic commissioner said the FCC had no alternative but to order the around-the-clock ban in compliance with the measure passed earlier this year by Congress. But she said she has "grave misgivings about the constitutionality" of the rule.

The recent court decisions, she said, "suggest that the courts would not uphold an outright ban on the broadcast of indecent speech."

The rule is to take effect 30 days after it is published in the Federal Register. It applies only to over-the-air radio and TV broadcasts and does not apply to cable TV.

In its order, the FCC noted that it previously had interpreted existing law to prohibit obscene programming at any time and indecent programming only when there was a reasonable risk that children might be in the audience. It said the courts also held that opinion.

But, the agency said, "the directive (of Congress) affords us no discretion . . . and we will now enforce the indecency restrictions 24 hours a day."

Diane Killory, FCC general counsel, said that although the FCC previously argued before the courts that indecency could not be removed entirely from the air, "a defense (of an outright ban) can be put forward."