scope:

The equipment specified herein is an omnidirectional antenna which radiates the control pulse/s utilized for three-pulse sidelobe suppression (SLS)/Improved SLS operation in the Air Traffic Control Radar Beacon System (ATCRBS). The input to the omnidirectional antenna is form the air traffic control beacon interrogator (ATCBI) portion of the ground station. This SLS omnidirectional antenna will be employed with en route radar antennas which have been modified with a NADIF beacon dipole feed to achieve a beacon directional elevation pattern with a sharp underside cutoff characteristics.

The principal objective of the elevation pattern of the omnidirectional antennas specified herein is to cover the elevation sidelobes of the NADIF directional pattern with the limited P2 peak power available from FAA beacon interrogators. In addition, the elevation pattern specified herein provides a relatively sharp cutoff at the horizon to control ground lobing.