In television, there are few rewards for being ahead of your time. Harry Shearer is at least seven or eight minutes ahead of his; even that can be a problem. His current Cinemax Comedy Experiment show, "It's Just TV," is as sly as Fu Manchu and as lovable as Ronald Reagan's dog, but it's a little unwieldy as a comic concept.

For the chance to see Shearer impersonate Charles Kuralt at full fatuous unfurl, one can overlook deficiencies. "It's Just TV" premiered on Cinemax very late Thursday and can be seen again tomorrow at 11:40 p.m. To appear only on Cinemax (HBO's younger brother) is limiting enough, but to be tucked away in Cinemax's attic is rather insulting. It does reinforce the theory that the only television worth watching is hidden in its fringes and corners.

"Just TV" was inspired by a report "60 Minutes" did last season on a convention of the National Association of Television Program Executives (NATPE), an annual event at which local station executives from around the country get together, drink heavily, ogle decorative maidens and buy syndicated programs for the following year's schedule. To truly appreciate a rickety piece of tripe like "Puttin' on the Hits," a big seller last year, one should probably watch it three sheets to the wind and with a showgirl on one's lap, approximating the state in which it was purchased.

Shearer lampoons "Hits" as part of his show. Those attending his fictional convention are offered a chance to snap up "Puttin' on the Spots," on which contestants lip-sync their favorite commercials -- naturally to roars of studio-audience approval. In the clip shown, a dazed rube manages to mimic every subtle nuance of a Victor Kiam shaver ad. Shearer does a cruelly accurate impression of Alan Thicke as the host.

Kuralt pops up, like a Macy's balloon, as the star of "At Home With Charles Kuralt," a producer's brainstorm that bypasses the copyright CBS owns on Kuralt's "On the Road" features. This show "reverses that concept," the syndicator brags; it has the pot-bellied windbag rummaging around his own house, except that, of course, his real house could not be used and so he rummages around a big prop.

Making his way to the bathroom, Shearer as Kuralt turns on the tub's faucet and exults in the rippling rhythms of running water. "You wouldn't even have to get in the tub," he rhapsodizes. "The sound itself could dramatic pause cleanse the soul." What deft and funny debunkery this is.

Shearer also impersonates Dick Clark (as host of "Dick Clark's Blooper News"), the curiously inescapable Casey Kasem, and Curt Gowdy, host of "This Week in Rock 'n' Roll." That show does a feature on a disc jockey who does play-by-play descriptions of MTV on the radio: "Videos for the Blind."

Others appearing include David Lander (formerly of "Laverne & Shirley") as a particularly tacky huckster, pushing "docutainment" and "infotainment" and other genetic mutations; Paul Shaffer, of "Late Night With David Letterman," as, more or less, himself; and Carl Gottlieb, one of the authors of the screenplay for "Jaws." Such an eclectic ensemble -- but then Shearer, seen for about half of last season on NBC's "Saturday Night Live," is an eclectic ensemble all by himself.

There are probably too many inside jokes about the TV business in this deservedly nasty half-hour, and Shearer is a little too cute, and a little too imprecise, about setting up the premise for unwary viewers. But at its heart and at its core, "Just TV" is just terrific. 'Young Comedians Special' ------

What is the state of our national comedy -- meaning not Congress and its search for dirty poetry, but the stand-up stalwarts who bravely face bistro rowdies? Not all that good if "Rodney Dangerfield Hosts the Ninth Annual Young Comedians Special" is any indication, and it certainly aspires to being an indication. The one-hour show, taped in May at Rodney's New York club, premieres on Home Box Office at 9:30 tonight.

Rodney himself is wonderful, the Heifetz of the stand-up comics, and to hear him reel off a few of his great self-flagellating zingers at the beginning of the show is heartening. No respect. "I fell asleep with a cigarette in my hand," Rodney says. "My wife lit it!"

Then come the young comedians, all of them white (but some of them doing racist characterizations), only one of them a woman, and she, Rita Rudner, more spacey than funny. Rudner is best on the subject of men, particularly their unfitness for subsisting on their own: "They live like bears with furniture."

Harry Basil tries to wring too many laughs from the word "groin" and then does a weak "Risky Business" imitation of Tom Cruise singing in his underpants. Bob Nelson's nearly interminable impersonation of a brain-damaged football player is deplorable. Richie Gold seems too reminiscent of David Brenner -- Lord knows one of those is enough -- and Maurice LaMarche's impressions need work, though it's refreshing to run across someone who does Dudley Moore, Christopher Lloyd and Barney Rubble.

Bob Saget tells the crowd, "Gosh, you're a wonderful audience, you really are," and pretends only to be feigning patronization, but when his so-so routine is over, he tells them, "You've been real nice; I had a good time." Ah, but it's the audience that's supposed to have the good time. Yakov Smirnoff, a Russian comedian, mostly does Russkie jokes, and Louie Anderson, a fat comedian, mostly does fatskie jokes.

But there is one discovery on the program: Sam Kinison, who spiels his shtick in an unsavory overcoat and frequently screams the punchlines at the top of his voice. He's particularly funny on the topics of trying to make oneself understood to the clerk at a 7-Eleven store, warning fellow males against the allegedly emasculating perils of marriage (he's quite literal on that one), and analyzing world hunger as it has long needed to be analyzed. Kinison would be grating for more than six minutes at a time, probably, but he's the one comic on the show with a little ferocity to him. The others are wimps.

Dangerfield is listed as executive producer of the special, with an assist from Estelle Endler. They're not responsible for the fact that these "young comedians" lack material, and often a point of view. Except for the occasional naughty word, most of what they say is innocuous enough for free TV. When you're paying, you want it funny, and you want it a little mean.