Why does television get so terrible in the summer? So that the new fall shows will look good by comparison. It's a sinister and effective network strategy.

Before the fall season can begin, though, the fall promo season, which started on all three networks in late June or early July, sprinkles the schedule with ads for the new shows to come -- basic, generic theme spots that make the whole idea of a new season seem riotously festive and delightful, and specific spots promoting specific shows.

It would be a promo season like any other right now if not for the way NBC has turned the tradition on its ear and the industry on its head--or something -- with a new, aggressive fall ad campaign under the direction of Steve Sohmer, the Burbank-based vice president in charge of "advertising and creative services" for the network. Until July 1, Sohmer held a similar position at CBS, but he says it wasn't enough of a struggle promoting the No. 1 network, so he went to No. 3 for a new challenge, and for a rumored $250,000 a year.

One of the first rules Sohmer broke was the one that says you don't name other networks in your promos -- that, indeed, you pretend there are no other networks. Sohmer has defied the tradition most noticeably in spots for "Taxi," the four-time Emmy winner for best comedy series that ABC moronically dropped from its schedule last spring (probably because it wasn't moronic enough).

Now Sohmer has "Taxi" regulars like Judd Hirsch, Marilu Henner and Danny De Vito starring in commercials that tell viewers to tune in "Taxi" on Thursday nights just like before, but with one difference: "Same time," they say to the camera, "better station."

ABC doesn't like that, of course. But an ABC spokesman in New York says the network isn't really miffed by the implication that it is an inferior network. "It's just that some people here question whether a negative approach gives a viewer a reason to watch something -- when you're saying, 'We're the best 'cause No. 2 isn't any good.' "

Even more unusual than subtly besmirching ABC (a network whose programming is awfully hard to insult -- let's face it) is the way the NBC ads concede that NBC is not exactly the nation's primary source of diversion. The network has languished in the tar pits for seven miserable years. In one "Taxi" spot, Hirsch tries to convince a cab driver to watch NBC and the cab driver scoffs, "Naw, they got nothin.' "

Says one longtime NBC veteran, "This is unprecedented. Openly we've gone out and said, 'Okay, we haven't been so good, we're No. 3, but we think we've got something better coming up this year.' " Because Sohmer is known for such fresh initiatives, the tale is told that when NBC affiliates heard that the wonder boy was coming over from CBS at their spring convention, they let out a long, spontaneous cheer.

Another cheeky Sohmer promo has "three-time Indy winner" Johnny Rutherford standing in front of a hopped-up orange hot rod that looks for all the world like the General Lee from the CBS smash "Dukes of Hazzard." Rutherford says, "Once upon a time, that was the hottest car in television," and then gives a spiel for NBC's upcoming "Knight Rider," which stars, Rutherford declares, an even hotter car. Warner Bros., which produces "Dukes," has objected to the spot, but it continues to run, and a CBS spokesman says, "We're not concerned about it."

Sohmer also accomplished the small miracle -- miraculous when one considers what a groggy old elephant the NBC bureaucracy can be--of creating instant promos last week when it was announced that NBC shows had been nominated for more Emmy awards (90) than any other network. The nominations were announced in the morning, and that night's "NBC Nightly News" included a promo Sohmer wrote and produced in Burbank that afternoon.

"Can you guess which network won the most Emmy nominations?" an actor in a tweedy sports coat asks the viewer. "ABC? CBS? shakes head . NBC! . . . If you guessed wrong, don't feel bad. Just watch NBC and feel good." Again it was implicit in the ad that NBC is anything but the No. 1 network.

From Burbank, Sohmer says the ad tells viewers, " 'Surprise, it's NBC that has the leadership this year.' It helps us position ourselves as a real creative force in the business in terms of initiating creative new product." Sohmer naturally believes that good promotion can build audiences for a network. "I have always maintained that outstanding promotion can make the difference of a rating point," he says. That's about 800,000 homes a week. Of course, that alone can't put NBC back into the race. NBC finished the '81-'82 season with an average rating three points behind ABC's and four points behind CBS'.

RCA chairman Thornton Bradshaw was quoted recently as saying that amounted to an annual revenue gap of $150 million.

One of Sohmer's big problems is that he can create the cleverest and most persuasive promos in the world, but he can only show them on NBC, where there are fewer viewers [for them.]"There is a fairly substantial differential," he concedes. But NBC does have the luxury of captive audiences for events like the World Series in early October and the Miss America pageant on Sept. 11, where promos can be flailed in the viewer's face.

Actually, flailing may not be the right word. The new NBC promos are insistent, but they aren't bossy and obnoxious, which has been the style at all three networks for years now. "The objective is to get yourself talked about in the right way," Sohmer says. "We're trying to appeal to people in a little different way than we used to do. Not the pie-in-the-face school of promotion. I think we've had enough of that."

This is the school that thinks viewers will watch a show provided the promos scream at them deafeningly enough about it. Or luridly enough, as in this promo for "Cagney and Lacey" on CBS last season: "Stay tuned as an undercover assignment as prostitutes leads Cagney and Lacey through a series of brutal murders -- next!" Sohmer was in charge when that one was doled out.

"We want to appeal in a little more intelligent way," he says now. "I think the public has got surprisingly good judgment. We've probably gone too far with the ranting and raving. I have been guilty of it in the past." Sohmer says the tendency was to cram spots with as much "physical action" as possible and says, "I think we've done too much of that."

Still, Sohmer's new spots for "Gavilan" probably won't win any awards for good taste. Since the show itself is now in the process of being completely overhauled, he has nothing much to work with but the title, which is also the name of the show's macho hero. So in the "Gavilan" spots, sexy models are caught whispering the name "Gavilan" or saying "ooh, Gavilan" as they recline on fur, in soap suds, in steam, or, in one case, underwater, with goldfish swimming by. One spot is called "Three-girl ooh Gavilan." It's three girls panting "Gavilan" in succession. One of them also says "ooh."

Meanwhile, the promo season rolls along with standard, but very well-produced, theme spots on each network. ABC's campaign is keyed to the line "Come on along" (they can't say "Still the one" because they aren't No. 1 anymore); spots feature extensive original production, not just scenes from shows. We see the casts of ABC programs romping through America, grabbing folks off the street for a grand march to the Love Boat, where they all presumably set sail together on the sea of life. The spots boil over with The Wholesomes and bring to mind the wax Americana of a good Pepsi commercial.

Those who saw moderately fascistic tinges in the mass-mobilization Busby Berkeley numbers of the '30s may see the same tinge in these spots, however; indeed, most of them open with Henry Winkler and Scott Baio, two ABC stars, arriving from the sky in a helicopter somewhat the way Hitler arrived from the clouds in an airplane at the beginning of "Triumph of the Will." Come to think of it, "Triumph of the Will" would have made a good fall campaign slogan, too. Maybe some network will use it someday.

"Come on along with ABC," a chorus sings, "We're reachin' out, it's you and me/Come on along, come on along, with A-B-C!" Each network will spend about $1 million on its fall campaign, and a lot of that money, an insider says, goes to pay for the music.

The CBS campaign, which was set in motion while Sohmer was still at that network, is built around the idea of "Great Moments," and a two-minute generic spot tries to link "great moments" of the CBS black-and-white past (photos of Lucy, Hitchcock, Sullivan, Gleason, and so on) with the present. A folksy kind of singer who sounds like Don McLean sings, "They brought laughter, they brought tears/Touched our hearts and warmed our years/With a moment's love, a moment's happiness/They came and went so fast, somehow they couldn't last/But the best are yet to come on CBS!"

This is followed by the refrain: "Great moments! (Looking good now!), Great moments! (Knew we could now!), Great moments, for you on CBS!"

NBC's theme, set in place before Sohmer arrived, is "Just watch us now," as in the importuning tune, "We're NBC (Just watch us), NBC (you'll love us), NBC, just watch us now." Of course, "Please watch us now" would probably be a more appropriate sentiment. But Sohmer thinks NBC chairman Grant Tinker really does stand a chance of pulling the network out of the mire, and industry observers seem to agree that NBC has sunk as low as it can go anyway. One insider in Burbank says some at NBC are so enthusiastic over the combination of Tinker and Sohmer that they're thinking in terms of moving from third place to second place this year and from second to first the year after that.

If that happens, Grant Tinker's next job would probably be either to balance the federal budget or to patch up the Mideast.

Another TV insider puts the promo season and the fall season that will follow it in a more cynical, and thus more rational, perspective. "The problem with promotional campaigns," he says, "is that people eventually get to see the programs."