A.M. - Amplitude Modulation
Transmission mode in which a carrier wave is
modulated so that its amplitude variations are proportional
to the amplitude of the audio signal. The resulting radio signal is
composed by the carrier itself and two
sidebands, extended to -3 kHz and
+3 kHz from it (for a maximum modulating frequency of 3 kHz, for voice transmission).
With AM you can use simple and cheap transmitters and receivers,
but the reception sensitivity is low, the use of transmitting equipment is
not efficient and the occupation of frequency spectrum is far from good.
For these reasons, amateur don't use AM any more, preferring instead
SSB to send voice signals.
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