Chet Forte can't conceal it any longer. The secret is out. If he doesn't use it on Monday Night Football this year, it's sure to be stolen.

For 18 months Forte has been seeing Mike Renfro's play in his sleep. You remember that one. January, 1980. The American Football Conference championship game. Houston's Dan Pastorini lofts a pass to Renfro in the corner of the end zone. Touchdown, Oilers. Well, not quite. The nearest official, in an apparent cataleptic fit, indicates nothing. After a summit conference, the pass is ruled incomplete. Houston loses to Pittsburgh.

"Nobody had that play right," Forte says. "None of the cameras were in the right position. Some of the replays NBC showed disagreed with each other. The only way anyone could have had it was with a camera on the opposite side of the field."

Forte's wish is ABC's command. For the Redskins-Patriots game this afternoon and all Monday, Thursday and Sunday nights until further notice, there will be a camera observing the scene from the 50-yard line opposite the press box. That gives Forte 11 cameras for your viewing pleasure.

"If I don't do this now, someone else will and I'll feel really bad about it," confesses Forte, starting his 11th year as director of Monday Night Football. "The time is right and we can certainly afford to do it. I'm not saying this will change the world. But we're going to come as close as possible to complete coverage of the game. If this camera works, I don't see how we can miss anything on the field."

The camera surely won't expire from overwork. Forte will go with it only when it gives him an angle unobtainable from any other piece of equipment.

"If I get one shot a game," Forte says, "it will be worth it."

The problem is the folks at home. The unknown is always frightening, and Forte is tampering with one of the foundations of the republic. So when the action on the screen seems reversed, do not panic. The difficulty is not in your set, antenna or eyes. That's exactly how it is meant to appear. Instead of the play running left to right, you'll see it right to left. That, of course, is how half the spectators in the stadium view the teams.

"I anticipate a lot of negative response from the fans at home," Forte admits. "Some people are going to be upset about it. At least half will probably say, 'What the hell is that guy doing?' But how long are we going to sacrifice better shots because of that? We'll break it to them gently, with lead-ins by the announcers and heavy graphics. People will just have to get used to it."

That admonition also applies to CBS. What you see and hear won't be what you've been getting. After years of covering the game as stodgily as its National Football Conference clients play it, CBS joins the 20th Century.

Fans' ears will hear the difference before their eyes see it. R.I.P., Pat Summerall and Tom Brookshier. Goodbye, Curt Gowdy and Hank Stram. So long, Vin Scully and George Allen.

Summerall remains the main play-by-play man. He will be joined for the first six weeks by John Madden, the network's biggest asset. When Madden's not with Summerall, he'll keep Scully company. Stram will spend some time with both Gary Bender and Scully. Brookshier moves to play-by-play, with ex-Bear Johnny Morris as his color man. Allen will team with Lindsey Nelson, whose jackets are almost as loud as the ex-coach's mouth. Gowdy is gone for good, the network having paid off the last year of his contract.

Caveat viewer: All pairings are subject to change halfway into the season.

"Rather than make a dogmatic decision, we decided to wait and see how the various teams work together," executive producer Terry O'Neil explains. "We felt that we could get more out of Summerall and Brookshier by splitting them. Familiarity breeds. You tend to get stale with the same partner.

"If change means taking risks, we're certainly taking some."

The biggest ones may not be immediately noticeable. After years of living on the 50-yard line, CBS finally has acknowledged that there are other places from which to show the game. In addition to the ubiquitous 50-yard line position, there now will be cameras on the right and left 25-yard lines, high end zone and low sideline, the latter via movable cart. There will be no fewer than five cameras at any game, an increase of one and sometimes two per broadcast. For national games, CBS will use six cameras and three replay devices, or possibly seven and four, respectively, depending upon the Sunday.

"There's no question we have to get to state of the art in our production," O'Neil admits. "We're going to standardize our production. We will look more like NBC and ABC.

"Our facilities have been behind the other two, but our people have been doing more with less than they have. It's easy to direct Monday Night Football with 10 cameras. It's not so easy with four cameras and an unfamiliar crew, as we've been doing. But I expect us to very quickly get to the norms set by the other two. It won't come easily and we'll make mistakes. But we will deliver."

NBC also has something to deliver: silence.

The network tried it for three hours last December during a Miami-New York Jets game, a.k.a. the Silent Bowl. Now it will try to be quiet less spectacularly but more frequently. As part of that plan, play-by-play announcer Dick Enberg will broadcast a game himself sometime during the season.

"We want to reduce the talking," coordinating producer Ted Nathanson says. "We've been working on cutting down the constant chatter since the Silent Bowl. Sometimes we achieve it and sometimes we don't. We'd like to do it more often this season."

NBC hopes to discover a star in the process, although the task will be made difficult if the announcers can't say as much. The closest people to household names are Enberg and Merlin Olsen, the best duo in the business. They return to head a competent but relatively unknown squad. Newcomers include ex-jocks Rocky Bleier, paired with Mike Adamle, and Jim Turner, who joins Merle Harmon. Keep your ears on play-by-play man Bob Costas and analyst Bob Trumpy, heirs apparent to Enberg and Olsen.

NBC also has moved to improve its visual presentation, although the effect may not be obvious. It has spent a considerable sum on upgrading its replay equipment and plans to use two such machines, rather than one, at as many games as possible. That won't be easy when the network has to broadcast eight games, as it does on three Sundays, or during the baseball playoffs, when priorities will shift.

But NBC will manage, as always. The success of its coverage is indicated by last year's ratings, in which, despite having smaller markets than CBS, it trailed by .2 points. Of course, it helps to have the AFC on your side.

"We have more exciting teams and we've worked harder at it," Nathanson explains. "I don't know what we can do that we already haven't done from a production standpoint. But I'm not sure it matters, because I don't think the average fan knows the difference in coverage, and it really annoys me.

"I think they see it in baseball, but I don't think they know we and ABC go for reactions to things. When they see it, they think it's great. When they don't see it, they don't miss it. I guess we'll just have to not miss anything."

Viewers will be waiting.