Washington's only all-business radio station, WPGC-AM (1580), will become an NBC Radio Network affiliate early next year.

The network did not renew its long-time local contract with WWRC-AM (980).

Katie Garber, a spokeswoman for Westwood One Inc., parent company of NBC Radio Networks, said the new affiliation will give better exposure to NBC's programming.

"They're going to carry more of our programs than WWRC did, so it's better exposure for our network," she said.

The agreement, which will go into effect February, 1991, calls for Greenbelt-based WPGC to run NBC's advertisements. In addition, the station agreed to broadcast NBC's hourly newscasts, News on the Hour, and two weekly features. WPGC also agreed to broadcast the network's late-night call-in show, Talknet. Of NBC's programming, WWRC was running only Talknet.

The switch surprised Don Hagen, editor of Hagen Media Research in Northern Virginia. While more of the network's programs and advertisements will be heard on WPGC, they will be heard by fewer listeners. In the latest Arbitron ratings, WWRC had seven times the audience share of WPGC-AM.

"If you just look at the facility alone, there's a big difference between those two stations. WWRC is a major AM station, and WPGC, even though it's had some life breathed into it recently with the all-business format, is still very small."

WPGC, which is owned by Cook Inlet Radio Partners Ltd., received approval from the Federal Communications Commission earlier this year to broadcast 24 hours a day. The station currently operates during daylight hours only.

"For us it means that we should be able to receive terrific programming," said Donna Francavilla, WPGC's program and news director.

"NBC has a wonderful reputation," she said. "Both Talknet and their news division have a wonderful reputation."

WWRC has been an NBC affiliate since 1925 when the network began. General Electric, which owns the NBC television network, sold the radio network to Westwood One in 1987. Since then, the network has lost several affiliates because of poor programming and management, radio observers say.

WWRC officials could not be reached for comment.