Bob Cobbins first thought of all-joke radio 19 years ago when he heard about the New York Telephone Company's dial-a-joke service.

"Who is going to pay a dime to hear one joke?" Cobbins remembers asking himself. About 40,000 people a day were, as it turned out, and it didn't take long for Cobbins -- who sold radio time for a group of Washington area stations -- to realize those numbers were no joke. He started collecting a library of comedy albums.

Cobbins applied for the broadcast license of WHMC in 1975, and at noon Jan. 31 this year, WJOK (1150AM) went on the air broadcasting humor 24 hours a day, seven days a week.

Joke jockeys intersperse shticks by such stars as Bill Cosby, Richard Pryor and Lily Tomlin with news, weather and traffic.

"From 4 a.m. to 10 p.m. we play material for a general audience," Cobbins says. "From 10 p.m. to 4 a.m. we play what we call blue humor, lacing in some contemporary stuff from comics like George Carlin."

The owner of America's first nonstop comedy station says the response from advertisers and listeners has been beyond even his expectations. Cobbins says he received 10,000 listener calls during WJOK's first month and several from station owners around the country who are considering duplicating Cobbins' format in their markets.