The LBJ Co., a Texas-based communications firm owned primarily by the family of the late president Lyndon B. Johnson, announced yesterday that it is donating its Fairfax City radio station, WEEL, to the George Mason University Foundation.

A university spokeswoman said the Northern Virginia school intends to continue to operate the AM radio station, which has a country and western music format, as a commercial station. "We have no plans for an immediate change, but that's not to say it will continue forever as country and western," she said.

George Mason President George W. Johnson said the station will become an independent source of revenue for the university and its programs in communications fields.

The LBJ Co. bought the station in 1977 from the OK Broadcasting Corp. for $912,000. Radio industry analysts estimated its current value yesterday at slightly more than $1 million.

Until he became governor in 1982, Charles S. Robb of McLean, the late president's son-in-law, was a vice president and director of LBJ, which also owns broadcast properties in Texas. Robb resigned from the corporation when he assumed the governorship.

The transfer of the station to the university foundation, the nonprofit fund-raising arm of the university, is subject to approval by the Federal Communications Commission.