Wisconsin yesterday became the seventh state to ratify the proposed constitutional amendment to give the District of Columbia full voting representation in Congress.

The state Senate approved the measure 28 to 4, along with a call for Congress to end "the sham of partial home rule" for the city.

The vote in Madison was the first by a state legislature since New Hampshire rejected the proposal on April 26.

Wisconsin joins New Jersey, Ohio, Michigan, Minnesota, Massachusetts and Connecticut in approving the measure. The amendment, passed by Congress in August 1978, would give D.C. two senators and one or two members in the House. For the amendment to become law, it must be ratified by 38 states by mid-1985.

The Wisconsin action was hailed a "particularly gratifying" yesterday by Sel-Determination for D.C., the national coalition that is working for passage of the amendment, because of the bipartisan support it received there.

Coalition Chairman Richard W. Clark said eight of the 12 Republican members in the Wisconsin Senate joined with Democrats in voting for ratification.

In the 10 states in which the amendment has been defeated, much of the opposition to the amendment came from conservative and Republican legislators.