A carrier to noise ratio of some 20 dB is required to give a " clean " picture.
2.
Typical signal quality measures involving noise are signal-to-noise ratio ( SNR or " S " / " N " ), signal-to-quantization noise ratio ( SQNR ) in " E " b / " N " 0 in digital transmission, carrier to noise ratio ( CNR ) before the detector in carrier-modulated systems, and noise figure in cascaded amplifiers.