WE THE people are being given the rare opportunity to repeat a colossal mistake made on our behalf about 30 years ago. In the early days of televison, the government should have reserved channels and set up effective funding mechanisms for a public TV system that could have flourished alonside commercial TV.

But it didn't.

Instead, in 1952, under pressure from commercial broadcasters who wanted the whole pie and the pan it was baked in, the FCC consigned most "educational" television to hard-to-get UHF channels (14 through 83), which most TV sets couldn't even receive for the next 20 years. And no means of paying for public TV was set up, so that three decades later, public television is still a scruffy orphan always begging for its next nickel and trapped in a perpetual indentity crisis.

Now comes the re-invention of the medium as something called cable television and the chance to make amends with a new, national, cultural, noncommercial, nonprofit program service. All it requires is $30 million and the willingness of the public TV establishment not to screw it up.

The idea comes from a 275-page, one-year, $116,000 study funded by the Carnegie Corp. of New York. That report calls for the founding of a new cable network named PACE, for Performing Arts, Culture and Entertainment.PACE could bring into homes all the cultural and offbeat programming that commercial TV won't bother with and that can't seem to get underwritten by corporations on public TV now.

For a $9 monthly fee, cable subscribers could add the satellite-delivered PACE signal to their TV sets and watch anything from Joseph Losey's film of Mozart's "Don Giovanni" to a new Broadway play like "Da" with Barnard Hughes to a Wagner festival from Seattle to punk rock from Greenwich Village. And after the programs played on PACE, they could be shown on regular publc TV. PACE subscribers would pay for the privilege of being there on opening night and would help subsidize production.

It would be television for people whodon't watch much television now because they think it is too dumb and because they can't stand all those insane commercials.

"It is an elitist service," concedes Nick De Martino, one of the report's three authors, "but what it says is, 'Okay, these people have the bucks, they're willing to pay for it.' So you'd have the money to get the productions made, and then later you could broadcast them on free TV for the nation. It's a sequence-of-play operation."

De Martino estimates that it woiuld take $15 million in Cpb loans plus $15 million in corporate and foundation grants to get the thing going, and that it would be a break-even proposition in its foiurth year. He says only about 750,000 subscribers would be needed to start, and that's only 250,000 more people than subscribe to The New Yorker. The audiences would be similar -- there's certainly no New Yorker of television now.

Buying PACE would be like subscribing to a magazine or a book club, and it would reserve a national cable channel for something truly cultural, occassionaly esperimental and noncommercial. It would be one channel safe from the jackals and a haven from the unending stream of movies and sports events on other pay cable channels.

"Obviously, consumers will not watch dreck forever," says De Martino. "There is a phenomenon going on where people who have cable are really quite pleased with the choice of 15 or 20 things that they never saw before. In Manhattan you get weird public-access channels, alphanumeric things on your screen (wire service news stories) like ticker tape, old movies from other cities, and it's not TV. It's cable. You really have to live with it to realize that it isn't the same as TV anymore."

So far about 16 million homes -- out of a total of 76 million American TV homes -- are living with cable. And in almost 9 million of those cable homes, a pay cable channel is purchased with an additional monthly fee. Experts predict -- well, experts predict about anything you want them to predict. But sober heads in cable think there may be 30 million cable homes by mid 1985 (when the number of TV homes will rise to 86 million) and that there could be 50 percent cable penetration by 1990.

Cable is hot television, busting out all over and ready to explode. That was made riotously clear at the recent National Cable Television Association convention in Dallas. There were 9,000 people at the convention -- which De Martino dramatically calls "high noon for cable" -- and many of them were from big, big companies now taking the plunge. These companies include Getty Oil, which has formed a partnership with four movie studios to set up a new movie channel to compete with Time-Life's successful Home Box Office (HBO) and other such service.

American Express and Warner Communications have teamed up to get into cable in a big way. And also making themselves known at the convention, wearing big Eye buttons with the promise that "You're going to hear from us," were representatives of the newly formed cable division of CBS. Yes -- CBS.

Imagine how wonderful it will be if the commercial networks, which ruined television the first time, get a chance to ruin cable television as well.

"The networks are right in the middle of it -- there is no argument anymore," De Martino says. "They recognize it, they've capitulated. They may argue at the FCC to prevent somebody else from doing what it is they want to do, but that's only because they want to get in first."

And what kinds of bold new programming were being hawked at the convention? Maurine Christopher of Advertising Age magazine summed it up in three words: "Movies, movies, movies." There just aren't going to be enough movies to fill all those cable channels, unless the cable channels start financing movie production themselves. Which is just what Time-Life is already doing.

A pay-cable service called Showtime had as its hotsy-totsy attraction a variety show starring Ed McMahon. Now there's a fresh face for you! HBO has already insulted its subscribers with early peeks at garbagey pulp like "Comdominium," scheduled to turn up later in syndication to regular stations, albeit with commercials added. Commercials don't hurt shows like that; they just spice them up with a little quick entertainment.

Producers trying to sell wares to cable TV do not have high praise for HBO. Some say HBO executives want nothing original, just sexier versions of the kind of pap already playing on regular TV. One recent HBO biggie: a comedy concert by the inescapable David Brenner. That's no choice; that's an ear-polluting echo.

This is why projects like PACE, aimed at something other than a mass-mass audience, should get a high priority, even if the project itself sounds a little too good or too crazy to ever come true. One problem will be, of course, public television itself. In effect it would be sanctioning its own rival, and public TV officials are insecure enough about their lots in life as it is.

"We're recommending that they create what they perceive to be their competition, in effect," says De Martino, who with Sheila Mahony and Robert Stengel, his partners, presented the PACE plan to a PBS convention on Tuesday. "Their reactions were mixed. Smart people think something like this is inevitable and that if we don't do it, CBS will, which is true. And dumb people say, 'Ugh! I might lose $35 in membership fees.' They don't realize that they're going to lose 'Live From Lincoln Center' and half the product they have in the first place if they don't do something."

Already there are signs that those who supply programs to PBS are going to opt for other buyers, like pay-cable channels, who wield bigger bucks. De Martino says of public TV, "They don't really have a choice" about the coming of cable, "so they might as well have some role in molding it." But De Martino also says the new service will have to be autonomous and not subject to the committee tyranny that keeps public TV usually several steps behind the times.

"It can't be part of PBS or it won't work," De Martino says flatly.

Some big cities are just now getting wired up for cable, which has been part of life in many smaller or rural communities for years. Cable was born of the need to import better signals for poor-reception areas, and as a business it didn't show any signs of skyrocketing until relatively cheap program distribution via satellite made it possible to set up a national network virtually overnight. Now, industry wisdom concurs, there is going to be no stopping it, and oddly enough, a recession could actually accelerate the growth of pay cable channels because people confined more to their homes will demand a greater diversity of home entertainments to choose from.

It would be a tragedy of the first order if cable TV were to end up ruled by exactly the same mentality that runs commercial and public TV now: The greatest good for the greatest number of Nielsen families, and who cares about anybody else? An idea like PACE could be one small step for cable, one giant leap for viewerkind.