At which altitude on V573 would the navigational signal of the HOT VOR/DME be unreliable?

The correct option reflects the operational characteristics of VOR navigational signals, particularly their reliability at various altitudes. VOR signals can experience limitations due to terrain and other factors, such as obstacles that can interfere with the line-of-sight propagation of the radio waves.

At lower altitudes, particularly below specific minimums, the possibility of signal obstructions increases due to the proximity of the terrain or structures. The APINE intersection, being at 3,000 feet, may encounter such interference along V573, resulting in unreliable navigational signals from the HOT VOR/DME. This altitude is critical because it is often where the terrain may rise, causing potential signal blockage.

In contrast, the other altitude choices listed, such as 2,700 feet at MARKI intersection, or 4,000 feet at ELMMO intersection, are not likely to face the same level of obstruction due to the elevation gains relative to surrounding terrain and the effective range of the VOR signal. Additionally, 1,500 feet at FARGO may still be within the range where signals remain stable and are less impacted by nearby geographical features.

The emphasis on altitude in relation to local terrain for reliable navigational signal reception is crucial for pilots, ensuring they can