[Premium-Rx] Filter phase response

[Gary Follett]

Actually, I agree with your approach. To get rid of the occasional 
heterodyne, a simple autoseeking DSP notch filter would be nifty. These 
can also be manually set so that they can track a CW signal and notch 
them out too.

Ideally, the DSP filter (whatever you want to use it for) should be 
inserted into the receiver's AGC line. That way, the unwanted signal 
does not desense your receiver. This is true for any accessory outboard 
filter, digital or analog, by the way.