ARRL Technician Practice Exam

What is a characteristic of VHF signals received via auroral reflection?

1. The signals remain stable and clear

2. The signals exhibit rapid fluctuations of strength and often sound distorted

3. The signals are consistently strong and undistorted

4. The signals have a very low frequency

The correct answer is: The signals exhibit rapid fluctuations of strength and often sound distorted

VHF signals received via auroral reflection are known for exhibiting rapid fluctuations in strength and often sounding distorted. This phenomenon occurs due to the unique properties of the ionized plasma that makes up the aurora. When VHF signals, which are generally in the range of 30 MHz to 300 MHz, travel through this ionized layer, they interact with it in a way that causes multipath propagation and scattering. These interactions can lead to variations in signal strength over short periods of time, resulting in a challenging reception experience characterized by distortion and instability. The auroral conditions create a dynamic environment that impacts the signal quality. This is why receivers often pick up these signals with noticeable fluctuations and distortions that can make them difficult to decode. Understanding this characteristic is crucial for operators who might be attempting to communicate or receive signals during auroral conditions, as they need to anticipate and manage the challenges presented by these variations in signal behavior.