"Dawnings of new eras" are not always recognized at the time. It was fortune for history that Lincoln preserved his Gettysburg Address on the back of an envelope.

The immediate impact of Ed Turner's Cable News Network on sports will not be felt at its launching today, unless your home is plugged into his system. Down the road, you will feel it in your pocketbook, when you realize that you can get your sports "fix" 24 hours a day.

A bit of self-analysis will remind you that at present you see most of the events you're interested in on free television, free if you don't count what you spend on a sponsor's products.

To dramatize how that is going to change, remember that you're not going to see the telecast of Sugar Ray Leonard's bout gratis June 20. It will cost $25 to $30 to see him defend his title against Roberto Duran in Montreal, on a closed-circuit telecast.

The conventional networks could not afford the risk, because of the nature of the sport. If the bout ended, say in the first round, a network could not recover its investment, since there would be no audience to see the commericals.

For the same reason, if Muhammad Ali gets around to fighting Larry Holmes, the purse demands will be so high that the bout also will be on closed-circuit telecast.

The specter of pay cable television will hover over National Football League club owners as they meet beginning Tuesday in Atlanta.

Major league baseball already shows some of its games on cable television.

The National Basketball Association could not get its "World Series" games on prime-time conventional television because of lack of appeal, but Turner's cable network has a diametrically opposite problem, finding enough programs to fill out a 24-hour schedule.

The National Hockey League has been snubbed by free television and may find its salvation in a selective audience on cable television.

Previously, the NFL prevented from switching its games from free television to pay television by government regulations that stipulated the league would have to first remain off conventional telecasts for five years -- and pass up the revenue in the interim -- before switching. That ruling has been struck down.

Now, NFL clubs are bound by a voluntary agreement to sell all their games as part of a league package, with every club sharing the revenue regardless of the size of the local television market.

Clubs in such metropolitan areas as New York, Los Angeles and Chicago were persuaded to go along so that smaller cities, such as Green Bay, would be able to compete for players.

But Al Davis of the Oakland Raiders is challenging the bylaws of the NFL in the courts, contending that he has the right to move the franchise to Los Angeles without approval.

It is expected that if Davis wins that right, he would pull out of the television agreement and try to make an individual deal for a pay-TV contract. If he were successful, other big-city clubs would be expected to follow suit.

In the past, when such a threat loomed, fans would compain to sympathetic congressmen, some of whom are Redskin rooters and live in the Washington area, and Congress would threaten penalizing legislation.

In fact, Congress told the NFL, on the blackout question, that league games had to be televised if they were sold out 72 hours in advance. But that experimental law has expired and the NFL now follows the policy only on a volunary basis.

Baseball may be less likely to incur the displeasure of Congress, because it has two television setups. It has a national contract in which all clubs share the revenue and the fans see a variety of attractions.

In any wholesale switch to pay television, baseball and football have eminent experts. Ted Turner of Cable News Network also is owner of the Atlanta Braves. Jack Kent Cooke of the vast Teleprompter system owns the Redskins.

When cable television achieves its full potential, the American sports junkie will pay his way as inescapably as his British counterpart, who is taxed on his television sets.

Tex Schramm of the Dallas Cowboys shot down a report that Roger Staubach would join the Penn State staff and replace Joe Paterno as head coach eventually, with Paterno limiting his responsibility to athletic director.

"I don't think Roger is the type," Schramm said. Staubach was thought to be in line to be an analyst on ABC college game telecasts before he joined the CBS pro football staff.

National Football League club owners will hear a report Tuesday in Atlanta on Edward Bennett Williams' dual role as president of the Redskins and owner of the Baltimore Orioles baseball team.

But neither Williams nor Jack Kent Cooke, owner of the Redskins, will attend the meeting. The club will be represented by General Manager Bobby Beathard and Larry Lucchino, secretary and general counsel.

In February, the NFL was informed that Williams was not in violation of the policy against control of franchises in two professional sports. Williams used to be the chief operating officer of the Redskins and Cooke, 86 percent stockholder, is now both. Beathard runs the club day to day, but that did not become a new role for him then: he had been filling it.

Another veiw on the feasibility of instant television replays to reduce officiating controversies: Coach Red Miller of Denver says, "I think there is a place for it. Horse racing would not be able to function without it."

Coach Marv Levy of the Kansas City Chiefs encouraged a guessing game about where 34-year-old quarterback Mike Livingston soon will be traded, and one reporter inferred it would be to Washington. Bobby Beathard later said Livingston didn't figure in the Redskins' plans.

There will be discussion at the NFL session about misunderstandings over the use of eye-hand-foot reaction timers; the concern over pirating of game telecasts by cable television systems, and long-range talks about possible realignment of the conferences on a tighter geographical basis because of the national energy problem and its effect on plane costs.

One club owner wonders why the Raiders are so eager to transfer to Los Angeles, recalling that the Rams and Pittsburgh Steelers were both unbeaten when they played when they played there last season, but drew only 65,000; not a poor crowd but 9,000 shy of capacity.

Steve Rosenbloom, fired from the Rams by his stepmother, has a new identity -- on the cover of the New Orleans Saints' spring prospectus as general manager with Coach Dick Nolan and No. 1 draft choice Stan Brock of Colorado. The day after the draft, offensive tackle Brock bet on Pass Protector at Jefferson Downs, and 8-to-1 shot, and won.

Don Heinrich's scouting report says there will be four wide receivers better than Lam Jones, Art Monk and Ralph Clayton in the 1981 draft-- Chris Colins, Florida; Mardye McDole, Mississippi State; Kenny Magerum, Stanford and Den Donley, Ohio State.