Public broadcasting is going to be studied again. It needs another study like Linda Lovelace needs a hormone injection.

Without casting any aspersions on the motives of the Carnegie Corporation of New York, which announced formation of a commission to study Public Broadcasting's future, neither the time expended nor the money spent will tell us anything that is not already obvious.

Public Broadcasting is in a shambles. Apart from Washington Week in Review, the MacNeil-Lehrer Report and Agronsky at Large (whose future is uncertain), the direction of news and public affairs is vague.

Apart from the excellent dramas imported from the BBC and occasional music specials, Public Broadcasting's programming is very thin, with little prospect for improvement. Only children's programming remains excellent and innovative.

The problem with Public Broadcasting is that its need for federal money gets it involved in politics. It becomes a political football because it has to court both the President and the Congress for money.

This allows Presidents to tinker with it in varying degrees. Congress, because it is obliged to vote the money needed to allow Public Broadcasting to function, also tinkers with it politically. And the people who run the Corporation for Public Broadcasting (CPB) are constantly engaged in political battles with the people in the Public Broadcasting Service over how much should be spent, and for what.

The result is that many bureaucrats in both bodies spend most of their time having meetings. These sessions accomplish little more than frustrating the many talented programmers who would like to get on with the creative process.

The Carter administration is understandably concerned about the future of Public Broadcasting. But the people in the administration responsible for broadcasting matters are gun-shy about doing anything in the way of reform that would smack of the excessive intervention practiced during the Nixon administration in both programming and bureaucratic structure.

There is every indication that the White House. sensitive to this problem, found the Carnegie Corporation's proposal for a new look a suitable mechanism for reviewing the situation.

My own instinct, however, is that the best way to shake up Public Broadcasting and give it some future direction is for Congress to formulate legislation to change the manner in which Public Broadcasting is funded.

The present system - public broadcasting must come up with $2.50 of nonfederal money for every $1 the federal government gives it - is no way to run a broadcasting service.

It forces Public Broadcasting into a dole mentality, begging aims from Congress, raising money by grants from corporations or holding those irritating membership drives that smack of the worst aspects of commercialism

The House subcommittee on Communications will be holding hearings this fall on a revision of the Federal Communications Act of 1934. The subcommittee has before it certain option papers on the future of Public Broadcasting.

The most important element is a proposal that a trust fund, somewhat akin to the Federal Highway Trust Fund, be established to provide long-term funding. This would allow Public Broadcasting to operate successfully, and would insulate it from White House or congressional pressure.

The option papers suggest several ways the funds could be generated: an excise tax imposed on television sets; a license fee for the use of television sets (a common practice in other countries); a fee imposed on commercial broadcasters for their use of the broadcast spectrum; a tax check-off similar to that used in financing presidential campaigns; or a pay service system in which the entire system is supported directly by viewers.

Whatever method is recommended the subcommittee is on the right track. The BBC and Japan's NHK operate pretty much free of political pressure, and that is the way Public Broadcasting should operate in the United States. It takes no 18-Month study by special commission to see that. It does take a decision by Congress that Public Broadcasting in its present form is not working, and that radical surgery is in order.