Which type of fading is observed near the limit of the skip distance due to changing angles?

• A. Absorption
• B. Skip
• C. Multipath
• D. Phase

Answer: (B)

The question refers to fading that occurs near the limit of the skip distance, where signals reflected off the ionosphere can experience variations in strength due to changes in the angle of incidence. This phenomenon is known as skip fading.

As radio waves travel over long distances, they can reflect off the ionosphere and create multiple paths to the receiver. Near the skip distance, where the reflected wave and direct wave may arrive at similar times, the interference between these two signals can fluctuate due to variations in angle, leading to constructive or destructive interference. When the angle changes (for example, due to atmospheric conditions or the position of the transmitting and receiving antennas), it can lead to a noticeable variation in signal strength known as skip fading.

Absorption refers to energy loss in the medium, while multipath fading refers to the effects of multiple signal paths contributing to fading, not specifically at skip distance. Phase fading, while related to phase shifts in the received signal, does not specifically address the phenomenon associated with skip distance. Hence, skip fading is the most accurate description of the observed effect near the limit of the skip distance.