What does the term "night effect" refer to in relation to Automatic Direction Finding (ADF) equipment?

The term "night effect" in relation to Automatic Direction Finding (ADF) equipment specifically refers to the phenomenon where non-directional beacon broadcasts can reflect off the ionosphere, significantly affecting the signals received during nighttime conditions. At night, the lower layers of the ionosphere become more conducive to reflecting radio waves, allowing signals to be received from greater distances than during the day. This can create challenges in accurately determining the direction of the beacon because the reflected signals may arrive at the ADF from multiple paths, leading to confusion in the readings.

In contrast, other options do not accurately define the night effect. Better reception due to atmospheric stability does not specifically capture the unique conditions affecting ADF at night. Ground stations transmitting at lower frequencies is not necessarily related to the night effect and can happen at any time. Improved accuracy during daylight hours is contrary to the phenomenon associated with nighttime signal behavior, as the night effect can lead to potential inaccuracies during dark hours due to reflections.