"I suppose I began to notice it on the day after Hitler's birthday," a South African Jew recalled. "Some Afrikaner hoodlums usually get drunk to celebrate it and go out and paint swastikas on the synagogues. This year, no swastikas."

The pressures South Africa's Jewish minority has traditionally faced in a society where racial prejudice is legally enshrined have been easing in recent years, at the same time that South Africa and Israel have been increasing their cooperation.

Both sides veil how deep that cooperation goes, especially in the military field. But it is deep enough to concern some liberal Jews about the contribution Israel is making to the white minority government's capacity and determination to resist drastic changes in is apartheid policies.

The American government has also become concerned. Unlike Israel, the United States observes an embargo on arms sales to South Africa.

Numbering 117,000 the Jewish community occupies an exposed position as a minority within the ruling white minority. Individually, South African Jews have been at the forefront of the liberal political movements that have campaigned against apartheid.

But the Jewish Board of Deputies has never joined the Roman Catholic hierarchy and other groups in formally condemning apartheid.

"We're too vulnerable as a group," a board member says, recalling that some of the white Afrikaner were interned here during World War II for pro-Nazi sentiments.

Despite his own record of wartime internment, Prime Minister John Vorster was warmly welcomed by the Israeli government in an April 1976 official visit.

Diplomatic isolation has helped drive South Africa and Israel closer together. Both are repeatedly and harshly attacked at the United Nations. After Vorsters' visit, a South African cartoonist presented Vorster of my best friends? Some of my only friends . . . . "

All black African states broke diplomatic ties with Israel when Israeli troops crossed the Suez Canal and moved into the Egyptian mainland and the African continent in 1973. The Israelis had attempted until then to maintain a low profile in their already important dealings with Pretoria, but after 1973 signs of much closer cooperation repeatedly have surfaced.

Israel has already supplied Gabriel guided missiles and at least two missile-carrying patrol boat to the South African navy, has licensed the manufacture here of the Uzi submachine gun and reportedly helped South Africa in developing a locally-made Mirage fighter-bomber.

Some South African Jews are conviced that Israeli military advisers also are turning up here. The two nations are known to share intelligence and tactical planning exercises of the two somewhat similar armies, diplomats report.

"I speak Hebrew and I've been to Israel several times," one young woman said. "A few weeks ago I was in a government building in Pretoria and heard these huge, military-looking young chaps speaking Hebrew. I talked to them for a while, but they never would say what they are doing here."

Mystery also surrounds the sudden release from a South African jail on Nov. 18 of Mattatiahou Cohen, a 22-year-old former Israeli tank commander, after he had served only seven months of a six-year prison sentence for raping of two South African women. Cohen was swiftly deported, traveling to Israel in the company of an Israeli general, according to one report.

The U.S. State Department is aware of low-level cooperation between Israel and South Africa on nuclear technology, according to American sources who declined to be more specific.

Israel has been reported to have nuclear weapons. South Africa appears to be working on an atomic bomb, these sources said. A white South African journalist has gathered strong indications of an influx of Israeli nuclear physicists into Pretoria over the past 18 months.

Tough statements on South Africa by President Carter during the election campaign have already made Israel sensitive to its high visibility here, according to reports from Jerusalem. An Israeli newsman told South African colleagues that Israel will now "draw less attention" to the relationship, but will not initiate changes.

"The Israelis keep anything on their arms sales to South Africa well away from us," An American diplomatic source reported. Israel's ambassador in Washington, Simcha Dinitz, already is advising Jerusalem to weigh carefully American reaction to Israeli ties to South Africa, according to one report.

The United States has moved to dash Israeli hopes of selling the Israeli-manufactured Kfir fighter to South Africa, reliable sources indicate. The Kfir uses engines and other parts manufactured under license from the United States, which must give its permission for the sale. The State Department vetoed a $180 million sale of 24 Kfirs to Ecuador by Israel on Feb. 7.

South African Jews make up the world's tenth largest Jewish community and are among the white minority's most highly educated and affluent members. Despite stringent new exchange controls, they have no difficulty remitting an estimated $20 million a year in donations to Israel.

"The Six-Day War did wonders," liberal political leader Helen Suzman says. "The 1967 victory engendered enormous respect for Israel and vicarously for South African Jews here, who have benefited."

A member of Parliament for the Progressive Reform Party, Suzman is one of apartheid's most outspoken foes and she is often bitterly attacked by Vorster's Nationalist Party for alleged "Communist" thinking.

But the invitations for her to leave South Africa and go to Israel, once heard in Parliament, and the crude anti-Semitic newspaper cartoons depicting her seem to be a thing of the past.

The Nationalists, who fought against Jewish immigration here during the 1930s and once had a clause denying Jews membership in their party, also have stopped calling attention to the prominence of Jews in liberal politics and high finance and business.

Despite such changes, South African Jews appear to be leaving South Africa at their highest rate ever, as are other English-speaking whites, according to unofficial estimates of 1976 emigration figures. Official totals are not yet available.

Last year, as black uprisings and police repression sharply polarized opinion here, 583 South Africans moved permanently to Israel, 40 per cent more than in 1975, according to Israeli statistics. Applications to the Israeli embassy in Pretoria indicated that the figure will double this year.

Those moving tend to be doctors, dentists or other professional people who can quickly establish themselves in a new country, according to Suzman and others. They tend also to be affluent and liberal on the South African spectrum. Not all choose to go to Israel.

"I thought he might go to Israel," a Jewish businessman said one day recently of his son, who had just left to live in Canada. "He said he would never come back until there was justice here, and that he couldn't go to Israel while it was helping feed this system."

"Jewish liberals do still face pressures" Suzman conceded. "But it's not the Jewish part now, it's the liberal. That's what brings the pressures. As for the Jewish community, I think the feeling is, do as you like but don't hold yourself out as the representative of the Jewish group."

Others stress their feeling that Jews should speak out as a group on apartheid because of their own history of being victimized while other groups remain silent. Rabbi Richard Lampart expressed that feeling in a prayer of penitence he read on Yom Kippur morning:

"O God of forgiveness, forgive us, pardon us, grant us atonement.

"For the sin we have committed:

"By forgetting we were oppressed.

"For the sin we have committed:

"By resisting social change.

"For the sin we have committed:

"By choosing to spend money for guns rather than for helping the poor."

Three hours after he delivered the prayer in the synagogue, security police searched Rabbi Lampert's house and circulated accounts of the search within his congregation.