Ronald (Dutch) Reagan, a former sportscaster, today paid a return visit to the airwaves of his old station, WHO. And for a while it was a disaster.

First, Reagan was 15 minutes late in placing the telephone call from New York to hook up with a popular morning talk show here. While listeners waited, the 50,000-watt, clear-channel station played commercials for Reagan's GOP rivals George Bush ("I bring you words from across America," Bush said in his ad. "We're going all the way") and Sen. Bob Dole ("Let's put a man in the White House who fights for farmers").

As the station's former sports director, Reagan might have expected a few soft pitches to be thrown to him when he came on the air.

But Susan Bray, the show's host, did not cooperate. She served up beanballs: Why' haven't you campaigned more in Iowa? Why didn't you come to the Iowa Republican debate? Why are you acting like a recluse? Why are you against the Equal Rights Amendment? Are you trying to conserve your strength?

Before Reagan, who will be 69 next month, knew what had hit him, one caller had said, "You don't sound like a young man." And a commercial had interrupted the proceedings to advertise a magazine with articles on "simple ways to restore potency to men who sex lives are over" and "10 ways to grow healthier as you grow older."

"It's a communist plot," moaned one aide listening to the broadcast at Reagan's state headquarters here.

"They're not that smart to play that one on purpose," consoled Ray Haige, Reagan's Iowa chairman.

Reagan had agreed only Thursday to appear on the show in an attempt to counter mounting criticism that he has not campaigned enough in the state. His timing was crucial. With four days remaining before Monday's precinct caucuses, all of the other major presidential contenders, with the exception of President Carter, launched last-minute blitzes across the state today.

Bush, the former U.N. ambassador and CIA director, with an outside chance of upsetting Reagan here, started out in the western part of the state and moved east. Sen. Howard H. Baker Jr. (R-Tenn.) started in the east and moved west. And John B. Connally set out on a 36-hour nonstop marathon swing through the state designed to demonstrate that at age 62 he has viability that Reagan lacks.

After 20 minutes on his old station, Reagan, a former actor, regained his normal relaxed state composure and managed to get off his standard denuciations of big government, high taxes, bureaucratic red tape, the evils of the Democratic Party and the Soviets. And he made a forceful plea for supporters to attend the GOP caucuses Jan. 21.

Asked if he would accept a Connally challenge to join the former Texas governor on his marathon, Reagan tartly replied: "Why should I help him publicize his circus trick?"

But before the hour was out, Bray got Reagan to renounce a statement made by his campaign manager, John Sears, and agreed to debate Carter on WHO. Sears had been quoted here as saying: "It wouldn't do any good to have him [Reagan] going to coffees and shaking hands like the others. People will get the idea he's an ordinary man, like the rest of us."

"Are you an ordinary man?" Bray asked the former sportscaster. When he said he was, she read Reagan the remarks by Sears. "I think that's an unfortunate statement, Reagan said. "We're all ordinary people. I'm proud to be one.'"

When it was over, Reagan, who plans to make his third and last brief campaign swing through the state Saturday, said:

"It felt good to be on WHO again, though nobody called me Dutch.'"

Meanwhile, Bush, looking lean and eager, arrived from New York for his 24th day of campaigning here, the longest any candidate has spent in Iowa.

As he stepped out of his Learjet, he was handed a copy of the Quad-City Times' endorsement. "Of all the candidates, who would you prefer to stand up and eyeball it with the Russians? George Bush," the Davenport paper said.

Across the state in the Missouri River town of Sioux City, sentiment was equally bullish. "Bush is going to win," said former Iowa congressman William J. Scherle.

But the candidate steered clear of predictions. "I have to do better than what is expected of me, and thus I don't want to be in the business of raising expectations," Bush said.

The Texas businessman brushed off his rival's attempts to mark him for first place "as very heartening. Neither Baker nor Connally gave me a snowball's chance in Hell six months ago."

Ralph Brown, a well-known Iowa Republican and an early Bush supporter, said, "Our goal is to break away from the rest of the pack and come as close to Reagan as possible."