The?detection?of?AM?radio signals is a diode application. The modulated?AM?carrier wave is received by the antenna of the radio receiver and is rectified

Frequencies?below approximately 10?MHz (wavelengths longer than 30 meters), including broadcasts in the?mediumwave?and?shortwave?bands (and to some extent?longwave), propagate most efficiently by skywave at night. Frequencies above 10?MHz (wavelengths shorter than 30 meters) typically propagate most efficiently during the day. Frequencies lower than 3?kHz have a wavelength longer than the distance between the Earth and the ionosphere. The?maximum usable frequency?for skywave propagation is strongly influenced by?sunspot?number.

Frequencies in the UHF range normally propagate by means of spacewaves

digital signals are only of form 0 or 1