The selectivity of the receiver is its ability to receive
the wanted signal and reject unwanted signals in adjacent channels.
Receiver selectivity is normally quoted by means of
a graph showing the output of the receiver in dB
relative to the maximum output, plotted against the number of
kHz off-tune, or by quoting some points on this graph.
For example, the selectivity of a HF receiver may be
quoted as -6 dB at 3-kHz bandwidth and -60 dB
at 12-kHz bandwidth. Typically, an AM receiver has a 3
dB bandwidth of about 9 kHz, an SSB receiver approximately
3 kHz, and an FM receiver's bandwidth is about 200
kHz. The adjacent channel selectivity of a radio receiver is
the responsibility of the IF amplifier.