President Reagan yesterday announced his intention to nominate Harry W. Shlaudeman, a career diplomat who was Reagan's special envoy for Central America, as ambassador to Brazil. Philip C. Habib recently took over from Shlaudeman in the special envoy post.

Shlaudeman has also served as assistant secretary of state for inter-American affairs and as ambassador to Venezuela, Peru and Argentina.

Reagan also intends to nominate Michael Novak as chairman of the U.S. delegation to a conference in Bern, Switzerland, on implementation of the "human contacts" provisions of the Helsinki Conference on Security and Cooperation in Europe. The goals of the accords signed in Helsinki in 1975 include freer movement of people and ideas between Eastern and Western Europe.

Novak, a scholar and writer on religious and ethnic political issues, is regarded as a prominent figure in the neoconservative movement composed largely of Democrats and former Democrats who support Reagan's policies. He formerly was the U.S. representative on the Human Rights Commission of the U.N. Economic and Social Council.

Other ambassadorial nominations announced by the White House include Patricia Gates Lynch to Madagascar, Vernon Dubois Penner Jr. to Cape Verde, John D. Blacken to Guinea-Bissau and Paul M. Cleveland to Western Samoa. Lynch, a producer with the Voice of America, served as press assistant to First Lady Pat Nixon in 1969. The other nominees are Foreign Service officers. Testing Their Medal . . .

Defense Secretary Caspar W. Weinberger was sufficiently impressed with military air traffic controllers who helped break the PATCO strike that he approved an award for them -- the Humanitarian Service Medal, according to a history of the strike published by the Air Force Communications Command.

More than 1,000 military controllers, the majority from the Air Force, were assigned to Federal Aviation Administration towers and control centers after the August 1981 walkout by members of the Professional Air Traffic Controllers Organization.

Two days into the strike, which was illegal under federal law, President Reagan fired about 11,500 civilian controllers. Military deployments to the FAA, made under a contingency plan in the works for almost two years, lasted through June 1983. Reenlistment bonuses of up to $16,000 were used to keep service controllers from jumping to FAA jobs.

The Air Force report concludes that the exercise had benefits beyond the airline industry. "The command's performance during the 1981-83 period helped to reverse an anti-military trend that had been growing throughout the country for at least the past 20 years" and Weinberger "recognized this fact" by approving the medal, it says. Educational Television? . . .

The Chronicle of Higher Education reports that supporters of legislation to extend the Higher Education Act of 1965, which concerns student grant and loan programs, are delaying consideration of the bill in hopes that it can be the lead act when cable television begins showing Senate proceedings in June.

Polly L. Gault, director of the subcommittee's staff, told the Chronicle, "We think it is a great idea. A lot of amendments that are selfish, people will be embarrassed to offer on television."

The Chronicle lays the supposed delaying tactic at the door of Sen. Robert T. Stafford (R-Vt.), chairman of the education subcommittee. But a Stafford aide denies it, saying that if anything, the senator is concerned about how quickly he can get the bill considered. If Stafford made any remark about tying the timing of the bill to the Senate's video future, the aide said, it was a joking attempt to increase the bill's chances of being considered as early as June. Spelling Trouble . . .

The nation's highest court is bedeviled by marijuana -- how to spell the illegal drug, that is.

One opinion contained this sentence: "At trial, Mrs. Briggs denied seeing any marihuana at that party or receiving a marijuana cigarette."

Henry Lind, the court's reporter of decisions, told The National Law Journal he thinks the court is "going to succumb to the letter J." He added: "I think everybody now agrees that J is the more popular."