15-HZ-BEARING INFORMATION

Figure 2-4.—Transponder output pulse train. 15-HZ-BEARING INFORMATION The rf energy from the TACAN transmitter is fed to the antenna central element, which has no The timing of the transmitted pulses supplies the directivity in the horizontal plane. Parasitic elements actual distance information to the aircraft. This leaves positioned around the central element are amplitude modulation as another medium for the electronically rotated (switched on and off) at 15 transponder to convey other information to the revolutions per minute. (See the section below on the aircraft. The TACAN beacon-transponder modulates OE-273(V)/URN antenna group). The distance the strength of the pulse to convey bearing information between the central element and the parasitic elements by producing a specific directional-radiating pattern is selected to obtain a cardioid radiation pattern. To rotated around a vertical axis. This signal, when an aircraft at a specific location, the distance data properly referenced, indicates the aircraft’s direction pulses appear to contain a 15-Hz amplitude-modulated from the TACAN facility. This signal and distance signal because of the rotation of the cardioid radiation data give a two-piece fix (distance and direction) for pattern. This pattern is shown determining specific aircraft location. and view B. in figure 2-5, view A 2-3