What Use Is An F-call?

What use is an F-call? I recently spent some time talking about the Grey Line, about the way it moves around and how it will help you make contacts along its path. If you recall, the direction of the Grey Line changes throughout the year. As the tilt of the earth affects the direction of the sun on your head, it also affects the shadow line that's drawn across the planet as sun-set and sun-rise occur at your QTH. Of course, you already know this. We experience this change as our seasons. So, if the Grey Line changes direction, the obvious question is, "Which way should you point your antenna?" If you are using a vertical, there isn't much pointing going on, but if you have anything that is rotating, even a mobile station qualifies, there is benefit in actually aligning yourself with the Grey Line. Of course you can look online and see a lovely Grey Line map and use that, but that does require that you have access to the Internet, or a phone with an App or some other technology. But you don't