Trying to understand selectivity

[tdenfuny]

If the specifications for a receiver is that the selectivity is, for exampel,

More than 2.1 kHz/-6dB,
Less than 4.0 kHz/-60dB

What does this mean?

Does this mean that when tuned to a frequency, the signals outside of 2.1 kHz are reduced by 6dB? What is the "less than" and "more than" referring to?

 

[bharvey2]

I'm a bit confused by the less than/more than too. I would expect it to mean that frequencies that are 2.1khz away from the tuned freq is 6db lower while those 4 khz from the tuned freq is 60db lower.

 

[nd5y]

Those specs are the shape of the filter skirt.
See Radio receiver filter specifications :: Radio-Electronics.Com or pages 15-17 of http://halifax-arc.org/sites/default/files/HamcourseReceivers.pdf