within the beam, adding to the natural accuracy of the conical scanning system. Whereas classical conical scan systems generate pointing accuracy on the order of 0.1 degree, monopulse radars generally improve this by a factor of 10, and advanced tracking radars like the AN/FPS-16 are accurate to 0.006 degrees. This is an accuracy of about 10 m at a distance of 100 km. Jamming resistance is greatly improved over conical scanning. Filters can be inserted to remove any signal that is either unpolarized, or polarized only in one direction. In order to confuse such a system, the jamming signal would have to duplicate the polarization of the signal as well as the timing, but since the aircraft receives only one lobe, determining the precise polarization of the signal is difficult. Against monopulse systems, ECM has generally resorted to broadcasting white noise to simply blind the radar, instead of attempting to produce false localized returns. Implementation for reflector antennas Monopulse antennas produce a sum signal and two delta signals. This allows angular measurement to be performed using a single receive pulse. The sum signal usually passes back down the waveguide used to send the transmit pulse. The two delta signals are elevation (up-down) and traverse (left-right). The sum signal corresponds with the antenna beam along center-line of the antenna. The delta signals are pairs of beams that are adjacent to the center-line of the sum antenna beam. The delta beam measurements produce plus or minus values depending upon the quadrant. The sum signal is created by a feedhorn structure positioned to maximize signal at the center of the antenna beam. The delta RF signals are created by pairs of antenna feed-horns located adjacent to the sum feed-horn (sum feed-horn not shown in the figure). The output of each pair of delta feed-horns are added together, and this creates zero output signal when the incoming RF signal is located at the center of the antenna beam. The signal strength from each delta beam increases as the aircraft drifts further away from the antenna center-line. For the waveguide image that is shown, a horizontally polarized RF signal arrives at the two feed horns to produce a left/right delta signal. The arriving energy from the RF wavefront is launched into both waveguide feedhorns. The RF signal from both feedhorns travels up the waveguide where the signals from the left and right feedhorn are combined.