Television asks a whole lot. We've been asked to believe that Rockford really could park a trailer on that prime piece of California beach, and that Ed McMahon really laughs like that.

But tonight at 9:30 on Channel 4, when Robert Conrad, in a two-hour pilot called "The Duke," starts a car chase in the snow and ends it running across the green grass, it's too much.

Maybe after enough years in Southern California, producers stop thinking that weather exists. Maybe they saw the gaffe and figured: "We were shooting on locating in Chicago, what do you expect?"

In any case, it's symptomatic of this latest attempt to collect interest on the bankability of Conrad ("Wild, Wild West," "Hawaiian Eye," "The D.A.," "Black Sheep Squadron.")

The situation is a confection of archetypes: Conrad playing a boxer-turned-private-eye to solve his manager's murder; the manager's black grandson who the Duke wants to turn out better than just a boxer; a rich girl who gets intrigued with the raw rugged honesty of it all (this is the city of Big Shoulders, after all); a nasty racist cop who learns his lesson from the Duke; and a hood with a heart of gold.

Those are the cards, and they'll be dealt out in various combinations on four weekly shows beginning April 11. Too bad that the most intriguing character, Crazy Tommy T, a villain played with a flip, grimy charisma by Michael Baseleon, is too weird to be a regular.

Being on location and all,the show is wonderfully free of endless car chases past palm trees, but otherwise the Hog Butcher to the World doesn't add a lot, except a skyline, a subway and those funny cop hats with the checkered bands. CAPTION: Picture, Robert Conrad in "The Duke."