> One of the great advantages of DSP is the lack of ringing in narrow
> bandwidths because of near zero group delay, and reduced operator
> fatique resulting from the noise reduction.
>
> Ian ZS6BTE
Hi Ian,
I don't understand how group delay is directly related to ringing. I
see no connection, unless group delay varies wildly with frequency.
A changing group delay in the passband may indicate the filter has
internal problems, either in design or construction.
Other than poorly designed filters, I see very little difference in
"ringing" between crystal and DSP filters.
People have the misplaced notion that CW will not "ring" in a DSP
filter. Rise and fall times are limited by filter bandwidth, and that is
what usually makes a filter "ring" on a smooth signal. A very
narrow filter, no matter what design, is going to "soften" rise and
fall times and make a signal "ring".
73, Tom W8JI
w8ji@contesting.com
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