A radio interferometer has been constructed at Haverford College as an aid to learning the fundamentals of radio astronomy. Its cost, both in cash outlay and in construction time, make it a feasible year-long project for an undergraduate. Its simplicity does not prevent it from being a useful instrument for instruction at the college or high-school level; among its capabilities are the measurement of the positions of at least four of the strongest discrete cosmic-noise sources, and the diameter of the radio sun.