TV's loose control knob

Deregulation - which has already reshaped such key US industries as airlines, railroads, and trucking - could soon be on its way to the nation's television stations. And if that happens, as many experts now believe it will, the impact could be far-reaching on what Americans are able to watch, or not able to watch, on their TV screens.

The broadcasting industry has long pushed for deregulation, a goal also favored by the Reagan administration. Last month the Federal Communications Commission's substantial deregulation of radio stations in 1981 was upheld in a federal appeals court case. Now the FCC - spurred by its chairman, Mark Fowler - is calling for a deregulation of the nation's commercial TV stations. The commission is seeking public comment on a number of options that would sharply curtail current FCC regulation.

The American public needs to be aware that proposed actions would, among other things, do the following:

* Modify or end the commission's watchdog role over programming, including public affairs and community service shows.

* Modify or end current requirements that at least 10 percent of all programs be nonentertainment shows and that no more than 16 minutes of commercials be broadcast in any one-hour period.

* Leave the matter of whether or not a station was presenting adequate public service programming solely up to possible rivals during a license renewal challenge. As it is, the FCC itself keeps tabs on such programming.

Present political ''equal time'' requirements are statutory in nature and would not be changed by deregulation.

There is a strong case that the broadcasting industry - indeed, all major industries in the United States - should be freed up from unnecessary red tape and bookkeeping requirements. But the broadcasting industry is quite distinct from other industries. For one thing, at least in the case of over-the-air TV stations, there are still a limited number of available channels. Moreover, the programming comes right into the home.

Mr. Fowler and other proponents of deregulation argue that such traditional reasons for regulating TV stations are no longer logical in an age of multi-channel cable TV and new satellite-to-home delivery systems. But is that yet the case when millions of Americans still do not have cable TV? At some point down the road, perhaps most households will have access to a genuine diversity of television outlets. But until that occurs, it would seem wise to move cautiously.

The approach of Congressman Timothy Wirth, chairman of a House subcommittee dealing with deregulation, seems reasonable. Mr. Wirth would link a long-range deregulation plan to a requirement that commercial TV stations be required to provide a certain amount of public affairs and local programming. By contrast, a deregulation measure that passed the Senate earlier this year would eliminate comparative renewal standards and would allow the FCC to make but a cursory analysis that a station's programming was meeting local needs.

Many stations have already found it more profitable to show repeats of popular network programs than to broadcast local programs, particularly programs serving minorities. At the same time, the professional codes of good taste pertaining to commercials have virtually been scrapped, although stations are still voluntarily policing commercials.

What it all adds up to is that, first, this is hardly the moment to peremptorily end FCC scrutiny of public affairs and local programs; second, more not less scrutiny is warranted to ensure there is any local access at all.