With a $390,000 loan from Averell and Pamela Harriman, the Democratic Congressional Campaign Committee bought a building on Capitol Hill last week that will be converted into a radio and television studio,

There, Democratic candidates will be able make their own campaign ads and tape their statements for broadcasting outlets in their home states.

Republicans have had a similar facility for about 10 years, and creation of the Democratic "media center" was one of the goals Rep. Tony Coelho (Calif.) set for himself when be became chairman of the committee last year.

Coelho said the facility will cost $1.2 million, and reconversion of the three-story building on C Street NE is already under way.

Radio operations are expected to start within a few weeks, and the video production may be ready by election day Nov. 2, Coelho said.

His committee will operate the center, making it available to senators and other Democratic big-wigs as well, Coelho said.

This building is separate from the plans for a permanent national party headquarters on Capitol Hill, which Democratic National Chairman Charles T. Manatt has been pressing.

Aides said there may be news on that front soon, as the Democrats continue to play catchup to their Republican rivals.