The Traffic Alert and Collision Avoidance (TCAS) provides a pilot display showing the range and bearing of nearby aircraft. TCAS obtains the bearing information by using an angle-of-arrival antenna. In the development of TCAS at Lincoln Laboratory, the first airborne tests were conducted using an Adcock antenna, which is a small square array of four monopole elements. This report describes an alternative antenna for TCAS, using three elements in the shape of a triangle. It is shown that the triangle antenna is less sensitive to receiver noise, and that improvement factor is about 10 dB.