Having a constant slope makes a lot of engineering sense. I believe, at
least at some bandwidths, the K3 offers both IIR and FIR (infinite and
finite impulse response filters). For data modes, FIR filters are
better, as they are linear phase filters. The skirt slope of such a
filter is directly proportional to the number of taps used in the filter
(the number of old samples added together). Having a large number of
taps increases the processing load on the DSP, so will be limited by the
need to work within the processing power of the DSP device. Also longer
filters mean larger group delays.
IIR's have variable group delays and ring, but can produce responses
that could only be approximated by very long FIR filters.
Incidentally, merging the roofing and DSP filter edges is likely to
compromise the good group delay, and lack of ringing, characteristics of
the FIR filters.
--
David Woolley
Owner K2 06123
On 16/11/15 15:59, char...@k5ua.com wrote:
I'm hoping that the constant slope you described is not the way the DSP
filters are implemented, because that would mean the 50hz filter has a
5.625:1 shape factor, the the 100hz filter has a 5:1 shape factor, the
200 hz filter has a 3:1 shape factor and the 400hz filter would have a
2:1 shape factor. To achieve better than 2:1 shape factor at 30dB per
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