| Amplitude Modulation
(AM) is the earliest form of radio transmission.
It applies a simple combination of a
carrier wave and a modulating wave (the
message). For example, a carrier wave
is,

The signal that we wish to broadcast
could be

The modulated signal is then


Frequency Modulation
(FM) uses the modulating signal to vary
the frequency of the carrier signal.
FM signals are generally more robust
and are capable of carrying higher fidelity
signals.
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 |
Guglielmo
Marconi (Italian,
1874-1937) was the first to
successfully transmit radio signals
across the Atlantic Ocean using
a telegraph, in 1901. |
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