Advocates and opponents of abortion have clashed for the past two days in Congressional hearings over proposed constitutional amendments that would annul last year's U.S. Supreme Court decision legalizing abortion.

The Senate Subcommittee on Constitutional Amendments, chaired by Sen. Birch Bayh (D-Ind.), heard testimony on two anti-abortion measures, one proposed by Sen. Jesse A. Helms (R-N.C.), which would ban all abortions, and the other by Sen. James L. Buckley (R-N.Y.), which would ban all abortions from the time of "implantation," five to seven days after conception.

Bayh had called for the hearings because, he said, "there are probably more strong feelings and deep convictions on this issue than any other since I've been chairman," the Associated Press reported.

However, Bayh was unable to find a senator who would testify in favor of the 1973 Supreme Court decision, which granted women the legal right to abortion during the first trimester of pregnancy, F. Woodman Jones '70, Bayh's chief legislative aide, said yesterday.

Last week, the Lowell House Women's Group initiated a postcard campaign urging congressmen and senators to vote against the amendments. Margaret C. Ross '76, a member of the group, said yesterday that 432 postcards were mailed from 10 of the Houses. Ross did not yet know the results of the campaign in Adams, Eliot and South Houses.

But an administrative aide to Bayh said yesterday that the mail is running totally in opposition to the Supreme Court decision.

Pamela Lowry, co-ordinator of the Constitutional Defense Project, a Boston-based pro-abortion group, said yesterday that nation-wide mailing campaigns have "just begun" because "up until this point citizens didn't seriously believe there was any danger of amending the Constitution."

"It is not logical in terms of politics for any congressman or senator to take any stand on the issue," she said. "What is important is what they think privately, and we will know that when the issue gets down to a vote."

Lowry said the longer the issue is "kept off the floor, the more chance we have of statistically proving the value of abortion to legislators and citizens."

Lowry said the anti-abortionists include various "right to life" groups which claim to be non-sectarian.