Radio waves are subject to reflections, even down in the AM band. Could be your power line acted as a reflector. Or acted as a larger antenna "coupled" to the radio antenna, thereby boosting the signal into the radio's circuits. I doubt the 110AC had anything to do with it, but that could be tested.
All radio waves are line-of-sight, it's just that they can be reflected by other things. The only reason you can hear distant radio stations is because the signals are being bounced back down to earth by layers in the ionosphere. This bouncing back and forth, up and down, is why you can hear some radio signals around the whole planet.
You move the extension cord, you change the whole
accidental antenna system.
People have reported "weird" things with their wireless mouses and keyboards, where moving the transmitter (mouse or keyboard) a couple of inches might kill the signal picked up by the computer. It could have been reflecting off another object in the room when it was working right, but that reflection gets lost when the "mirror" or the mouse gets moved too far.
I sometimes have trouble with my over-the-air television signals when my neighbor opens his steel front door, or when the trees outside get wet. (All our front doors are steel jacketed.)
Not only that, but signals can be "directed" as well as reflected.
In the famous Yagi antenna, the long element is the reflector, the middle element is the "driven" element, meaning it's what's connected to the radio, and the shorter element (up top in the pic below) is the "director."' The signal is strongest in the direction of the "director" element and forms a beam. Hence, "beam antenna."
There doesn't have to be an actual electrical connection between these elements. This is a Yagi made out of steel measuring tape.
The dimensions and spacing of the elements is critical, but calculable.
Many pictures of the "Little Boy" Hiroshima atomic bomb shows the Yagi antenna for the radar fuse. It's toward the nose, but the driven element (the one in the middle) is a folded driven element for impedance-matching purposes. The detonation was set for a 600 meter airburst. There was also a barometric fuse.
I always found it personally amusing that the Yagi antenna, as shown here on the Little Boy atomic bomb, was invented by the Japanese. Tee-effing-hee-hee.
Terry, 230RN
Pic credits in Properties