Gov. Charles S. Robb came home to Northern Virginia Saturday night to join an enthusiastic gathering of Fairfax County Democrats at a reception in Springfield.

Robb, Lt. Gov. Richard J. Davis and Attorney General Gerald L. Baliles made their first appearance together here since their inauguration last month.

Strolling musicians played the haunting folk melody "Shenandoah" as the three worked their way through the crowd at the Springfield Inn after Robb cut a yellow satin ribbon to open the new hotel.

Steven David Stone, Democratic chairman for Fairfax's Lee District, said the victory of the three "represents the new coalition, which is a majority of the people in Virginia: business and labor, young and old, black and white. I expect this new coalition to keep on growing."

Some horseplay ensued when Bob Travers, an Alexandria businessman, teased Ginny Lehner, vice chairman of Fairfax County Democrats, about her resemblance to a member of the Board of Supervisors.

"I still say you look like Sandy Duckworth," Travers declared. "People are always saying that," responded Lehner. "I think I could work one side of the street for her."

"She could, that's true," added Duckworth (D-Mt. Vernon).

Duckworth's husband Don, an official with the Smithsonian, appeared to enjoy the banter but turned serious when the subject of the federal budget came up.

"The Smithsonian is very labor-intensive," he said. "All these little cuts hurt. For instance, a museum like Natural History has a budget of $50 million, and over 90 percent of that is people.

"So far we've been able to absorb costs, mainly through attrition, but I'm very much afraid that we're going to have to start riffing people."

Two former Carter appointees to the Office of Management and Budget--James McIntyre, who was director, and Hubert "Herky" Harris, who worked Capitol Hill--also expressed worries about the proposed budget.

"It concerns me greatly to see such large deficits that appear to be with us for many, many years to come," McIntyre said.

Referring to David Stockman, President Reagan's OMB director, Harris said, "The father of the balanced budget is submitting one that's so unbalanced it's sort of surprising."

Meanwhile, at the Knights of Columbus Hall in Arlington, the county's Young Democrats were hearing West Virginia's Gov. Jay Rockefeller exhort them to pursue unity.

"I don't want to overemphasize that Virginia is a little backward," Rockefeller said, "but West Virginia passed the ERA in 1972." His audience cheered.

"There must be reunification between the Young Democrats and the rest of the party," Rockefeller added.

The honored guest of the evening was former 10th District congressman Joseph L. Fisher; the theme was the 100th anniversary of Franklin Delano Roosevelt's birth.

Balloons, streamers and signs declaring "Repeal Prohibition Now" and "We Want Roosevelt" decorated the hall for the dinner-dance.

"I'm especially pleased to be part of a winter banquet honoring FDR," Fisher told the group. "I first saw him in Cambridge in 1932, and only then realized how disabled he was."

Fisher, who will serve as secretary of human resources in the Robb cabinet, got a laugh when he said he and wife Peggy "have gone to the holy city . . . of Richmond."

Concerning his appointment by Robb, he said, "It's an exciting prospect and I'm going to enjoy the challenge of it very much."

New officers installed at the banquet include Nancy J. Sedmak, president; Susan Maloney, vice president; Amy Bruno Tate, secretary; and Steve Lewis, treasurer.