A coil for magnetic resonance imaging operates in a transmit mode with multiple loops locked together in a phase relationship like a birdcage coil to provide a uniform transmission field, but in a receive mode like a phased array coil, each coil operating independently to produce a separate signal for reception by the MRI machine. Phasing of the coil during transmit mode is provided by a ring resonator controllably coupled to the loops. Controllable coupling is provided by a series of current limiting elements interposed between the resonant ring and the loops of the coil.