Sherman W. Pratt, a northern Virginia civic activist described by his attorney as "Arlington's Man of La Mancha . . . a challenger of lost causes," was fined $2,000 yesterday for filing false tax documents.

Pratt, 57, who twice lost races for the Arlington County Board, was also given a six-month suspended sentence and placed on three years probation by U.S. District Court Judge Albert V. Bryan Jr. in Alexandria. He could have received three years in prison.

"I feel better, this has been a terrible ordeal," said Pratt of 1511 S. 20th St., Arlington, after the hearing.

Pratt pleaded guilty May 8 to misdemeanor charges of altering a property document by $20,000 and submitting a check for $200 purporting to verify, a medical bill, according to a spokesman for the Internal Revenue Service.

Frank W. Dunham, Pratt's attorney, told the judge before sentencing that Pratt, who had played a leadership role in the community and had a clean record, had been humilated by his conviction. In calling Pratt "Arlington's Man of La Mancha," Dunham was referring to Don Quixote from the Spanish town of La Mancha who tilted at windmills in the novel by Miquel De Cervantes.

Pratt, former president of the Arlington Ridge Civic Association, has long championed South Arlington, which he claims has been neglected by the county government. Pratt is a nonpracticing lawyer and highly decorated veteran of World War II and Korea.

Dunham told Bryan the documents were filed by Pratt during a period of stress in Pratt's life.