The Dalton Group Inc., owner of WXTR-FM (104.1), has sold WXTR-AM (1560), the 1,000-watt, daytime-only component of the oldies station, to Michael Burns, a Delaware broadcaster.

William Dalton, president of the company, said this week, "We had seriously thought of separating the two stations. We had always simulcast the two. But we decided this was the route we wanted to go." The La Plata, Md., station had been on the market for six months and was sold for $290,000, said Dalton. In June 1981, when Dalton bought the AM/FM combination, the company paid $2 million.

Burns, who has 16 years' experience in broadcasting and currently is the general manager of two stations in Georgetown, Del., said he bought the station because of its location in Charles County. "I am really fascinated with the county. It is growing rapidly and is underserved by the media. No radio station or newspaper covers it on a daily basis," said Burns, the head of Charles County Broadcasting Inc. After approval of the sale by the Federal Communications Commission, which is expected by Feb. 1, Burns plans to have three full-time news people and a pop music format similar to WMAL-AM (630).

In the last year Dalton has invested $500,000 in improvements to the FM operation, moving its studios and offices from La Plata to Marlow Heights and installing a new antenna and second transmitter. "We are going to continue the route we are going. We found our niche, and we are now probably one of the oldest formats in the area," said Dalton. What Are You Doing . . .

WKYS-FM (93.9) and WWRC-AM (980) will be offering periodic broadcasts from the city's New Year's Eve party on Pennsylvania Avenue Tuesday night. Just before midnight WKYS intends to go live from the James Brown concert in front of the Old Post Office Pavilion.

Deirdre Daly, staff director of the Mayor's Committee to Promote Washington, said the organizers try to rotate the stations and the two stations were selected because of their "broad audience."

"We just wanted to make sure we hit a variety of people," Daly said. "WRC is jazz-oriented and they have Felix Grant, a longtime Washingtonian. WKYS has deejays who are really hot and are playing the kind of music we are featuring outside."

The major sponsors for the evening are the Mayor's Committee, Miller Brewing and Mid-Atlantic Coca-Cola Bottling Co.; each contributed $30,000. The stations absorb the cost of the productions and WKYS, said Daly, also made a cash contribution.

WKYS' schedule begins at 6:30 p.m. with Candy Shannon holding forth at the shops at National Place. Stratus, an 11-piece band, will be playing. At 8 p.m. Melvin Lindsey will start the program outside the Pavilion. Listeners to WKYS will then hear four hours of uninterrupted music with feeds from National Place and the exterior stage of the Pavilion. Then the Brown concert will be carried until 1 or 1:30 a.m. Going home, WKYS' listeners can hear the top ballads of 1985 with Kevin James.

Another reason WKYS was selected, said station Promotions Director Joe Alfenito, is its success with the city's Riverfest on the Southwest waterfront last summer. "We just gave the mayor a good package of promotional announcements, the talent we have and our drawing power as proven by Riverfest," said Alfenito. He says the cost to the station is "not a whole lot more" than the $5,000 WKYS spent on Riverfest. "But it is two times the preparation because of the two remotes."

Felix Grant of WWRC will do reports four times an hour from inside the Pavilion from 8 p.m. until 1 a.m. The station will air Cab Calloway and the D.C. Jazz Workshop Orchestra live at approximately 11 p.m.

In another live event, Larry King will be broadcasting "an old-fashioned New Year's Eve" from the Jefferson Hotel. As in the last six years, King will not be live at midnight but will have a delayed celebration when his show starts after the news at 12:06 a.m. Included on the program, which is heard on WTOP-AM (1500), will be band leader Peter Duchin, Baltimore Orioles owner Edward Bennett Williams, baseball legend Joe DiMaggio and singer Brown. King promises old-style announcements, such as "and now, from the downtown Jefferson," a microphone hooked up to the Duchin orchestra for live cutaways and multiple announcements of the New Year as the show goes through four time zones. "I can't remember when I had a New Year's off unless it was a Saturday or Sunday," said King.

Elsewhere on Tuesday night:

*WBMW-FM (106.7) -- The B-106 countdown from 3 p.m. until midnight.

*WWDC-FM (101.1) -- From 4 p.m., a countdown of the top 101 songs of '85. The station also is hosting two parties, one at the Crystal City Hyatt with the Adam Smasher band and another at the Hyatt Arlington. Both start at 9 p.m.

*WPKX-FM/AM (105.9/730) -- From 5 p.m., the KIX country countdown, lasting 28 hours.

*WRQX-FM (107.3) -- From 6 p.m. until midnight, the Q-107 countdown.

*WGAY-FM (99.5) -- From 7 p.m. to 6 a.m., "Sound of New Year's," a dance-music special.

*WWDC-AM (1260) -- From 8 p.m. to midnight, "Sounds of Sinatra"; from midnight to 3 a.m., Big Band with Eddie Gallaher.

*WAMU-FM (88.5) -- From 8 p.m., Big Band program with Robert Bamberger.

On New Year's Day:

*WRQX -- From 10 a.m. until 6 p.m., a countdown with Casey Kasem.

*WKYS -- From 8 a.m. until 6 or 7 p.m., a countdown of the top 93 songs.

*WPKX-FM -- From 9 p.m. until midnight, "Country Music Countdown '86," with Lee Arnold and Lee Greenwood.