### Advantages of FSK

FSK is a constant envelope modulation, and hence insensitive to amplitude (gain) variations in the channel and compatible with non-linear transmitter and receiver systems. The detection of FSK can be based on relative frequency changes between symbol states and thus does not require absolute frequency accuracy in the channel. (FSK is thus relatively tolerant to local oscillator drift and Doppler shift.)

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Disadvantages of FSK

FSK is slightly less bandwidth efficient than ASK or PSK (excluding MSK implementation). The bit/symbol error rate performance of FSK is worse than for PSK.