September 18, 1981

When Irwin L. Jacobs, the 39-year old Minneapolis multimillionaire, elbowed his way onto the Pabst Brewing Company board, he was viewed as an unfriendly interloper, at best. As owner of about 10 percent of Pabst's outstanding shares, Mr. Jacobs, who made his fortune by buying failing or bankrupt companies, first demanded last summer that he be named chairman and that four of his associates be named directors. He settled for a lone board seat for himself. Now, Mr. Jacobs is giving up that seat. But in doing so, he has issued heated statements indicating that his battle with the nation's third-largest brewer - behind Anheuser-Busch Inc. and the Miller Brewing Company - is far from over.

''I woke up in Chicago and I'm going to sleep in Washington,'' Thomas Sowell said cheerfully yesterday as he descended to street level in a crowded elevator. Mr. Sowell, the conservative black economist, social theorist and polemicist, had just given a luncheon speech for 80 people at the private Century Club on West 43d Street. They had gone to hear him because Mr. Sowell's most prolific period - now - happens to coincide with the advent of Ronald Reagan and the resurgent political and economic conservatism across the country that Mr. Reagan's Administration is said to stand for. Two books by Mr. Sowell - ''Markets and Minorities'' and ''Ethnic America'' - have just been published, to much praise from fellow conservatives and a lot of criticism, some of it bitter, from fellow blacks and from liberal intellectuals. As for his travels, Mr. Sowell is indeed on the run. His home base is the conservative Hoover Institution on War, Revolution and Peace at Stanford University, in California. At lunch yesterday, Mr. Sowell sat next to George Gilder, one of the Reagan Administration's favorite economists for the unabashed defense of capitalism he presents in his recent book, ''Wealth and Poverty.''

New construction of single-family houses in August plunged 16.4 percent from July to its lowest level since the Government began keeping records more than two decades ago, the Commerce Department reported today. In addition, new construction of all categories of housing fell 10.7 percent to an annual rate of 937,000 during the month. The rate was only slightly above the 9 04,000 rate of February 1975, the department sa id. The only lower rate was the 843,000 of October 1966.

International Opposition to the sale of Awacs radar planes and other air warfare equipment to Saudi Arabia gained as a clear majority of the Senate publicly lined up against President Reagan's arms sale proposal. While the development did not spell final defeat for the President, it clearly threatened the possibility of a serious political defeat for him and a possible setback in relations with Saudi Arabia. (Page A1, Col.6.) The Russians demanded the silencing by Polish authorities of an ''unbridled'' anti-Soviet drive by Solidarity and other dissidents that had reached ''dangerous limits.'' (A1:5. )

James L. Emery, the Assembly minority leader and a potential Republican candidate for Governor, charged today that, based on a comparison with California taxation figures, New York State and its local governments lose $3 billion a year through faulty collection of sales taxes. In an analysis comparing New York tax collections with those of California, Mr. Emery charged that New York collected some $1.7 billion less than the nation's most populous state, even after taking into account differences between the two states' tax structures and the sizes of their economies. By extrapolation, Mr. Emery said at a news conference, tax evasion cost local governments an additional $1.36 billion. ''The honest taxpayer who is paying taxes is being victimized by the Carey administration's inefficiency,'' he said.