[Elecraft] Filter Question

[Jim Brown]

Hi Wilson,

The response of the DSP IF filters combines (cascades) with the roofing 
filters; when both are the same bandwidth, their skirts fall off much 
more sharply (the rolloff is equal to the sum of the two filters). When 
one is much broader than the other, we get only the skirts of the 
narrowest one.

This is generally true of all filters, whether digital or analog, except 
to the extent that the combined phase shift modifies the total response.

73, Jim K9YC

On 9/9/2020 10:24 AM, Wilson Lamb wrote:
> Would someone please explain the relationship between our plug in filters (K3) and the variable filter response provided by our width control.
> As I understand the situation, the plug in filters we buy are roofing filters, used to prevent intermod from strong signals outside the pass band.
> Is there more to it?