Talk:On-off keying

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This paragraph is somehow misleading.

OOK is not very spectrally efficient due to the abrupt changes in amplitude of the carrier wave. At low to medium signalling speeds, this can be mitigated by adjusting the rise and fall rates of the carrier's amplitude. At high speeds, more efficient modulation modes (such as frequency-shift keying) are normally used instead.

The abrupt changes in amplitude of the carreir wave can be viewed as a square wave modulation which leads to frequency expansion. However, this is inherited in most of the digital modulation scheme such as FSK, ASK and PSK. Therfore, going for FSK does not solve the problem. Besides, Frequency-Shift Keying is not intended for a specturally efficient modulation.