quote:

Originally posted by chas257:
In a nutshell; the ionosphere is made up of several layers, the closest to earth is the “d” layer. When the sun rises in the morning it begins to ‘charge’ the particles in the air at this layer & the particles absorb the medium frequency radio waves; once the sun sets in the evening the particles are no longer charged and the radio waves then bounce off the higher ionosphere layers which allow the signals to travel much father.