Gov. Charles S. Robb, expressing dismay about Virginia's "demoralizing" unemployment picture, called yesterday for new government and business efforts to spur growth of computer, communications and other high-technology industries in Northern Virginia.

"Obviously, we want to encourage a variety of developments in the field of high technology," Robb said. "We need a major redirection."

Robb outlined his high-technology aims during an impromptu news conference in Springfield, where he addressed about 500 members of the Fairfax County Chamber of Commerce. In his 25-minute speech, he hailed Fairfax as "the high-technology center of Virginia" and said the county's economic development programs would serve as "a model" for study by state officials.

At the news session, Robb said he may propose "a very modest amount" of additional state spending for education or other high-technology programs in an attempt to encourage expansion of computer industries and to attract more high-technology companies to Virginia. But he declined to suggest specific plans, saying, "I don't want to put a dollar amount on it."

Robb's call for increased high-technology development followed his establishment last July of a 29-member task force on science and technology, which is studying proposals for luring more computer firms to the state. The task force, headed by T. Justin Moore, board chairman of Virginia Electric and Power Co., is expected to make recommendations within a year.

In addition, Robb suggested such appropriations may face obstacles. "It's politically not very popular because it's always viewed as 'Oh, the businesses can support themselves' and what have you."

Nevertheless, he argued, "Up to a certain point, it makes good business sense to spend money to make money." He suggested that modest state appropriations may prompt increased business investment, which may in turn lead to more jobs, additional tax revenues and other benefits.