Below FL180, en route weather advisories should be obtained from an FSS on which frequency?

Below FL180, the appropriate frequency to obtain en route weather advisories from a Flight Service Station (FSS) is 122.0 MHz. This frequency is designated specifically for such communications and is widely used for private pilot operations, ensuring that pilots can receive timely and relevant weather updates while in flight. Utilizing this frequency allows pilots to maintain situational awareness regarding meteorological conditions that may impact their flight, thus enhancing safety.

The other frequencies listed are typically used for different purposes, such as distress communications, standard recreational pilot operations, or other aeronautical needs, but are not primarily designated for obtaining en route weather advisories. Therefore, the use of 122.0 MHz is essential for pilots seeking weather information below FL180, reinforcing the importance of knowing the correct frequencies for operational communications in aviation.