Figure 1-11. Cardioid Pattern Resulting From Inner Parasitic Element

INSTRUMENT FLIGHT RULES WORKBOOK

CHAPTER ONE

Wires

On Outer

Rotating

Cylinder

Wire On Inner

Stationary

Rotating

Central

Cylinder

Element

Reference

Pulse Disk

Drive Shaft

Figure 1-10 TACAN Ground Beacon Antenna Design (Azimuth)

Magnetic North

Fixed Center

Element

Inner Parasitic

Element

Coarse Pattern

Figure 1-11 Cardioid Pattern Resulting From Inner Parasitic Element

3. Determination for bearing. To determine the aircraft's bearing from the station, a phase

angle must be electronically measured. To measure the phase angle, a fixed reference is

established. This fixed reference is a 15-pulse-per-second nondirectional signal normally

referred to as the main reference bearing pulse. One main reference pulse occurs with each

revolution of the antenna when the peak of the cardioid is at a magnetic direction of 090. In

addition to the main reference pulse, eight auxiliary reference pulses also occur during one

revolution of the ground beacon antenna. Therefore, a reference pulse occurs each 40 of

INTRODUCTION TO AIRBORNE NAVIGATION AND COMMUNICATIONS

EQUIPMENT AND PRINCIPLES OF OPERATION 1-15