The paper describes the design of a laboratory model of the multiport Eleven antenna and explains how the sum and difference patterns are generated in this model. Its tracking performance is investigated through both simulation and measurement. This paper also introduces a practical method for determining the scattering parameters of an antenna with multiple ports, when it is excited for both sum and difference beams, without using a feeding network with sum and difference ports. The monopulse tracking capability may open up interesting opportunities for using the Eleven antenna in satellite communications over one or more of the L-, S-, C-, X- and Ku-bands.