An optical signal that propagates along a conventional waveguide is back reflected at waveguide terminations. If the waveguide permits only one-way propagation, this back reflection cannot take place; the optical signal undergoes a nearly 100% conversion to radiation modes. We examine this termination effect in a recently suggested nano-scale one-way plasmonic waveguide, and its properties as a perfectly matched nano antenna. Since one-way structures are inherently non-reciprocal, our antenna possesses different transmitting and receiving patterns, and a dynamic beam-forming functionality. These properties may be used in applications requiring dynamic directional selectivity that differ in transmit and receive modes.