"Spike-at-the-Mike" O'Dell's morning show was interrupted today so the president of the United States could get a tryout as a radio call-in host on KSTT-Davenport.

The tryout started badly.

"Oh, hi. Who is this?" asked one of the first persons who was called.

"I think you're Debbie Brown," the new man at the mike said with a broad grin.

"I am," she said.

"My name is Jimmy Carter," the president said, his eyes twinkling.

For the next 45 minutes, the president talked over the airwaves of the quad cities area of eastern Iowa and western Illinois. It was quite a show. It was, after all, the first time a president of the United States had ever hosted a call-in show on KSTT.

The last time a president ever visited the quad cities area was in 1952 when Harry Truman passed through a whistlestop campaign tour for presidential candidate Adlai E. Stevenson.

While today's show was based on a classic call-in format, in reality no one called in. The station selected those to whom the president would talk from a list of 100 people who had indicated that they would like to talk to Carter. Then the station called them.

Sitting behind two microphones in the small news offices of the radio station, Carter was almost an ideal talk show host. He was smooth. He was folksy. He called everyone by his first name. And when he saw his daughter through the window, he said, "I think I'll have to go. I see Amy peeking."

When he finished, Carter, who sat through the show in shirtsleeves, said, "I had some good questions."

Actually, there wasn't a tough one in the lot. Several of the 13 persons who called simply wanted to tell the president they thought he was doing a good job. One man was so excited about having Carter on the other end of the line he could barely utter a word. So he called his wife and child to the phone to say hello.

Another person, Jaye Cessar of Rock Island, Ill., said she appreciated the sacrifices the Carters were making. "It's not a sacrifice to serve as president, it's gratifying," Carter quickly replied.

Another caller told him the biggest problem the nation faces "is the morale of the American people."

This is exactly what the president wanted to hear. And it is the reason he did this show today and has schedules a live, two-hour broadcast from the White House Oct. 13 on National Public Radio.

The talk show and four hours of other activities here were an imagemaker's delight. Carter was photographed speaking in front of the Delta Queen steamboat, kissing babies, holding an ear of corn and dumping a bushel basket of corncobs into an experimental energy saving machine.

Eleven-year-old Amy autographed American flags and posed for pictures on a miniature John Deere tractor the company gave the president.

Not once during the day did he have to face the issues that dominate power centers in Washington. And when reporters shouted questions at him about U.N. Ambassador Andrew Young, who resigned under fire, and Middle East negotiator Robert S. Strauss, Carter refused to comment and turned away.

The Quad-City Times suggested that the president should have stayed home. "It honors any community our size to have a president of the United States visit it," it said in an editorial. "Thus we welcome President Carter.

"But, to put it bluntly, we wish he had remained in Washington, it continued. "There is much to be done there. Inflation continues to riddle our pocketbooks. Solutions to our energy woes are still evasive. The president has just concluded making major changes in his Cabinet, and he should be close at hand to assess the impact."

Carter, however, saw little of this feeling expressed in Davenport, the 16th stop on his seven-day "vacation" cruise down the Mississippi River from St. Paul to St. Louis aboard the Delta Queen.

Everywhere he went he was surrounded by hundreds of well-wishers wanting to touch him. When he encountered protesters shouting, "Jimmy who, Jimmy when. We won't be fooled again," he waved and said he would see them later.

Today's call-in format fits Carter's needs ideally as he struggles to boost his poor ratings in public opinion polls. It showed him at his campaign best; homey, unconcerned and noncontroversial.

It was not that the questions were bad. They weren't. Some, in fact, were quite insightful, far different from the prickly kind he gets in Washington, always seeming to focus on that day's headlines.

But the questions were general, the kind the skillful politican can turn to his own advantage. And there was little time for follow up.

Jaye Cessar, for example, asked that, if Carter could choose three things he'd like to accomplish in office, what would these three things be? He replied that he'd like to guarantee security of the nation, leave office "with no American in danger of losing their lives in combat" and that he'd like to see "peace in other parts of the world."

There were other not-unimportant subjects. One person was worried about foreign imports. Another wanted to know how the Carters like Davenport. Cindy Wolse of Davenport asked: "I'm just a little person, OPEC to me is just another four letter word that we talk about at the dinner table. I need to know something I can do specifically."

Sitting in the KSTT newsroom with only news director H. L. Jackson, program director Jim O'Hara, press secretary Jody Powell and this reporter present, Carter was thoroughly at east. An elegant silver water pitcher was placed at his right, but he didn't bother to take a sip from it.

The only time he appeared to be really worried about a question was when Keith Royal of Davenport warned that he was a high school debated. It turned out that Royal wanted to know why Congress had been tardy in passing the president's energy proposals.

Carter was ready for the question. Oil companies, he said, have tremendous influence in Congress. "Since I've been president, I've tried to build up consumers as an opposing force," he said.

Spike the Mike O'Dell said he thought it was a great show. The young disc jockey cornered Carter in the hall as he was leaving, and threw his arm around the president. "Could I get a picture for my grandchildren?" he asked. Carter readily agreed. "My future grandchildren, thank you," O'Dell said.

Later, Carter went to the headquarters of the John Deere Co. in nearby Moline, Ill., for a demonstration of energy-saving devices the company is working on. Wednesday he is schedules to appear before a town-meeting in Burlington, Iowa.