The broadcast and electronics industries are praising the Federal Communications Commission's endorsement of advanced television systems with enhanced sound and picture quality.

The FCC last week declared the new systems in the public interest and approved some preliminary rules for bringing them into American homes. But the commission said many technical and procedural problems still must be ironed out.The "high definition" TV systems will be designed to have the clarity of movie film and the sound of compact discs. They probably will not be available from the U.S. broadcast industry before 1993, according to an official of the National Association of Broadcasters.

Michael Rau, the NAB's vice president for science and technology, said the FCC made a "strong commitment to bring advanced TV to the public. They seemed to reaffirm support for free, over-the-air broadcasting.

"But the commission must solve the difficulties of delivering the system over broadcast outlets."

In a series of preliminary rulings, the FCC said:

-Existing broadcasters and stations are best equipped to bring the new system to viewers.

-Advanced television programs must be received on existing television sets so viewers won't have to replace their equipment.

-If additional frequency space is needed, it should be found within existing VHF and UHF television bands. The FCC found that looking for frequencies outside those bands would delay the service, and noted that bands now suitable for the systems are in use for other purposes.

Mark Rosenker, spokesman for the Electronics Industry Association, said his group of electronics manufacturers is "pleased that the FCC's decision has begun to define the complex issues regarding high definition television so that the American public will be able to enjoy the benefits within a relatively short period."

The FCC sought public comment on three options for using the airwaves for high definition TV. There would be a 60-day comment period and 30 days for replies.

FCC Chairman Dennis R. Patrick and Commissioner Patricia Diaz Dennis supported all the commission's findings and proposed options. Commissioner James H. Quello dissented on grounds the commission acted prematurely.

Quello said the FCC based its preliminary findings on computer projections and should have waited until the technology was tested and developed.

But Patrick said the technology to improve picture resolution exists today, and the FCC should spur further research and development.

His view was supported by Dennis, who said: "Some urge us to move more slowly, to wait for more evidence before acting. That is tempting, but delay creates significant costs."

Although Patrick said the preliminary rulings would "put the U.S. in the forefront of the international quest for new TV technology," the Japanese have been working on an advanced system for two decades.

They plan to offer a preview with broadcasts of the summer Olympics to high definition TV sets in about 50 big-city department stores throughout Japan.

The picture on a standard television set in the United States is produced by a signal that scans more than 200,000 dots on 525 lines. The Japanese system has 1,125 scanning lines.