By DAVID HINCKLEY
Daily News Staff Writer

Alan Fredericks was just a radio rookie when he got to WADO in 1961 and found himself on the air next to Douglas (Jocko) Henderson.

But this much he grasped at once: "Jocko was one of the most talented people I ever worked with. I mean, he was really talented.

"Those were the days when jocks could do their show — pick the music and everything — and Jocko did the whole package. I don't think he ever turned his microphone off. When he played a record, he'd sing the bass parts or he'd talk back to the lyrics.

"He was bigger than life, a marvelous personality, and just as charismatic off the air."

Jocko Henderson died Saturday in Philadelphia. He was about 70 and the feeling was pretty much unanimous yesterday that his passing leaves radio sadder and poorer.

"To guys like me, it was the Jockos and Eddie O'Jays who created the kind of personality radio we wanted to do," says Ken Webb, morning host on WWRL. "They had an innovation you don't hear today."

Jocko came to WLIB in 1954, when rhythm and blues was still an exotic and dangerous sound, and he added his own touches: He arrived on a rocket ship and he spoke in rhyme, a good-natured precursor of hip hop.

"Sayin oo-poppa-do / How do you do / Dy-no-mite! / Now on with the flight."

"I thought he was the greatest thing in the world," says Dan Ingram of WCBS-FM. "He wasn't the only one who did rhyming introductions, but no one did it better. And he played the damned sexiest records a 12-year-old kid could ever want to hear."

Jocko stayed on New York radio for a decade, finishing up on WADO. He hosted wildly popular shows at the Apollo and broke the color barrier by getting his own daily show on Ch.13.

"He broke a lot of ground for black jocks," says Hal Jackson, the fellow pioneer who brought Jocko to New York and became his longtime friend. "And he was also a wonderful person. Whenever I did something in the community, he was there."

Even after Jocko moved on — he had entered radio in the first place against the wishes of his educator father — he loved the medium. He came back for several WCBS-FM Rock and Roll Radio Greats reunions, and 'CBS program director Joe McCoy says he got right back into the rhythm: "I loved just sitting there watching him work."

"To project to your audience that you're having fun is something even a lot of successful radio guys can't do," says Ingram. "Jocko did it. He will be missed."