Preselectors are very broadband; they just knock down 80m when you're
listening to 40m, say. They're on the order of MHz.

Passband is well attacked by selectable sideband (to get to the side
away from the interference), or a brickwall audio filter in the
special case of an interfering SSB signal offset in the direction
of the SSB sideband you're listening to. Passband is order of kHz.

Heterodynes are knocked down with an audio notch.

General background hiss type noise can be gotten at with a DSP.
--
Ron Hardin


On the internet, nobody knows you're a jerk.