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Analog
AM/FM/pulse
transmitter
Analog
AM/FM/pulse
receiver
Modulator
(modem)
Demodulator
(modem)
ASK ≡ Amplitude Shift Keying
FSK ≡ Frequency Shift Keying
AASK ≡ Audio Amplitude Shift Keying
AFSK ≡ Audio Frequency Shift Keying
OOK ≡ On-Off Keying
PAM ≡ Pulse-Amplitude Modulation
PPM ≡ Pulse-Position Modulation
Simple transmitter and receiver
Insensitive to carrier-frequency errors
HISTORICAL
PATCHING!
Large radio bandwidth BR >>C
Poor spectral efficiency C/B<<1bit
Inefficient non-coherent receiver
20dB...50dB worse than Shannon