First it happened with radio, then with cable television. Now programming aimed at specialized audiences, or "narrowcasting" as it has become known, is being tried by commercial UHF stations as a strategy for reaching more affluent viewers.

In San Jose, Calif., KSTS, a newly licenced UHF station that can beam its programming throughout the San Francisco Bay area, is attempting to attract well-heeled viewers by becoming a business information station. "We decided to go after the high-income elite who could help us attract advertisers," says station owner John Douglas. KSTS is syndicating its financial programs to three other UHF stations that are trying to draw the same audience.

UHF narrowcasting isn't new. Since the 1960s the SIN Television Network of New York City has been feeding Spanish-language programming to stations around the country. It now serves 21 UHF stations and expects 200 satellite interconnected affiliates this summer. But unlike those who have gone after ethnic minorities or built their station images around religious or sports formats, KSTS is shooting for a different -- and, some believe, harder to reach -- slice of the market.

Each day the station produces two hours of business programming in the morning and another hour in the afternoon. To augment these shows, KSTS receives seven additional hours from Financial News Network of Santa Monica, Calif., a producer of investment-oriented shows.

Hundreds of UHF stations around the country rely on syndicated reruns to fill their air time. But with cable and pay TV coming on strong, Douglas believes that narrowcasting may be the only hope for smaller UHF stations to compete successfully in the big-city markets. There, he notes, it's common for a dozen or more VHF and UHF channels to jockey for market share. "If you're not the second or third independent in a major market," he says, "it makes sense to specialize."

Although Douglas thinks UHF narrowcasting based on business programming can succeed, many experts expect it will be a lot more difficult to pull off than ethnic or sports formats. Among other reasons, the major TV networks and cable systems are themselves beginning to carry more high-quality business shows.

Recognizing there may be a rocky road ahead, Douglas, a former securities analyst, is hedging his bets. Last March, he signed an agreement to transmit KSTS programs over the Tulsa, Okla.-based Satellite Program Network, a cable network that reaches 4.7 million households in 46 states.