Angkor, here’s a reply to your inquiry about the WMAL signal:
“Like all radio stations, our power and signal patterns are dictated by the FCC. We are required to lower our power at sunset, whenever that comes, and change the signal broadcasting pattern (meaning in what direction our signal is going out). In the winter months, that means the switch comes very early this month (January), its 5:15pm. Thats why youre losing the signal at that moment, depending on your location, and the strength of the antenna in your radio. That change in power will move to later in the afternoon/evening each month until June, when it starts going back the other way. The same thing happens in the reverse direction in the morning hours Grandy and Andy cant be heard in some areas until we power up at sunrise, which, obviously, comes later in the morning during the winter months. This is true of all radio stations, and is the law. Its not up to us. Why? The AM signal reacts differently in the daytime from nighttime, and stations very far away that broadcast on our frequency 630 AM might have their signal overlapping with ours, or vice versa, so were all required to adjust. At least, thats a non-engineers understanding of whats going on.
Thanks for listening to 630 WMAL!
Jerry Klein”
Thanks for the info. I suspected it was an FCC/licensing issue and not something they did voluntarily.