We present a realization of an optically controlled pulse-burst position modulator to be used for a radio-frequency photonic circuit aiming to produce beam forming for a Radar-transmitting antenna. The configuration uses a set of fiber ring resonators that contain erbium-doped fiber amplifiers. By controlling the pumping in each loop, the gain of the doped fibers is changed, which results with a change in the resonators' finesses. In the end of each optical path, the optical signal is sampled and converted to an electronic signal while an electronic subtraction is performed between the outputs of the two resonators. Because each resonator has different and controlled finesse, the subtraction results in an output pulse burst with varied position.