There are no records for this sort of thing, but it has undoubtedly been a long time since a modern U.S. president has isolated himself so completely for so long as Ronald Reagan has done since arriving at his California ranch Aug. 6.

But the Reagan vacation mode, judging by the past nine days here, appears to be no more than an exaggerated version of the Reagan White House mode.

The president has no love for detail work, and his willingness to delegate authority is well known. So, while Reagan's aides like to portray him as keeping in touch with developments while vacationing, they do not pretend that the president is spending large amounts of time on government business.

Still, there is no evidence that the conduct of government stutters while Reagan is at his ranch.

The president receives telephone calls from his deputy chief of staff Michael K. Deaver, sometimes several times each day, and takes calls from other administration officials from time to time, but he appears so far to be content not to initiate many calls.

When reporters on Tuesday began to ask White House deputy press secretary Larry M. Speakes whether the president was placing any calls, the only one it was certain Reagan had initiated had been to Pete Rose last Monday night to congratulate him on setting a new National League record for base hits.

The next day, Speakes was able to report that Reagan had telephoned Transportation Secretary Drew Lewis to discuss the air controllers' strike.

Each day the president receives written reports on national security affairs, transmitted electronically from the White House to a temporary office headed by Deaver in a Santa Barbara hotel and then flown to Reagan's Rancho del Cielo by helicopter. Well-informed sources said, however, that the paper flow to Reagan is down to a trickle.

Protectors of the Reagan image do not worry as some earlier White House staffs have about the president appearing to relax his grip on government while vacationing. But the staff is greatly concerned that the president do well when he makes a public appearance, and they were delighted by Reagan's performance Thursday when he emerged from his privacy at the ranch to hold what amounted to a news conference.

News conferences have been the weakest part of Reagan's public performance as president, his advisers think. The president has appeared uncomfortable in the traditional White House news setting and has stumbled on several questions, particularly on foreign affairs.

Since television networks usually carry news conferences live, all of Reagan's uncertainties have been broadcast. Other presidents have timed their meetings with the press to capture the largest possible evening television audiences, but Reagan's three news conferences in the White House have all been held in the afternoon when the audience is much smaller.

At the ranch, a live telecast was technically impossible and reporters were not certain in advance that the president would take more than a few questions as he signed his budget and tax bills. But he answered all questions the reporters had and ended in a joking exchange that included Nancy Reagan.

Reagan appeared completely at ease and, adopting the presidential "we," joked, "This is the first morning we haven't ridden. We decided instead that we'd come out and be ridden."

The president, however, never dropped the reins. Afterward, his aides canvassed reporters on how the president had done, certain that the only possible answer was that he had been very successful.

The informal news conference at the ranch seemed to provide his advisers with a new way to meet reporters' demands for access to the president while also meeting their goal of presenting Reagan only in forums where he does well.

Pressed on when Reagan would hold a formal meeting with reporters, the usually patient Speakes first remarked that reporters had run out of questions during the session at the ranch. Later, Speakes ran out of patience. "We will have a news conference when we get ready to have one," he said.

From a public relations viewpoint, Reagan's appearances even in the White House are rationed so that the television networks have little choice what film to use each evening.

Symbols are also popular and Reagan will make what appears to be a purely symbolic trip to an aircraft carrier this week. The president will spend about five hours on the Constellation off the California coast, permitting the White House press corps to send out film, photos and stories of Reagan aboard ship at a time when he seeks to stress his commitment to defense.

The small amount of impromptu Reagan the public sees is limited here to long-lens shots of tiny figures moving about on the ranch. When Reagan first learned that the networks were watching him through lenses from a neighboring mountain, his reaction was to make a joke.

Reagan asked what his aides thought would happen if the next time he went out horseback riding he suddenly clutched his side and tumbled off his horse.