Which instrument is a direction-sensing device using two loops oriented 90° apart to determine direction?

• A. GPWS
• B. Goniometer
• C. GNSS receiver
• D. GPS antenna analyzer

Answer: (B)

Understanding how direction is determined with radio signals helps: two loop antennas placed 90 degrees apart form a simple direction-finding setup. Each loop responds to the magnetic field component of the incoming RF wave, and the signal strength varies with the source’s bearing relative to the loops. When the transmitter lies along one loop’s axis, that loop receives the strongest signal while the other is weaker; by comparing the signals (or rotating until a null is found), you can deduce the direction to the source. The instrument that interprets these two orthogonal loop signals to indicate bearing is a goniometer.

Ground Proximity Warning System serves terrain awareness and avoidance, not direction sensing. A Global Navigation Satellite System receiver determines position by satellites, not direction from orthogonal loops. A GPS antenna analyzer tests antenna performance, not bearing to a source.