Dick Rollema wrote:
Narrow bandwidth filters do not have to ring provided they are of the
phase-linear type (constant group delay in the passband).
I use a home made passive phase-linear filter with a bandwidth of 30Hz and
centre frequency of 1000Hz. It can pass up to 24 wpm without trouble
(unfortunately the operator can't ...) The filter has four tuned circuits
with coils in large ferrite potcores.
Harry, PA0LQ, has designed a similar filter of the active type using 4
opamps. If you are interested in his design write to:
H.A.A. Grimbergen, PA0LQ
Lijtweg 1202
2341 HE Oegstgeest
The Netherlands
73, Dick, PA0SE
Are they a "Bessel" design? All analogue filters have some trade-off
between skirt selectivity, phase response and ripple in the passband.
Murphy's Law applies too, in that the phase linear types (least ringing)
also have least skirt selectivity. Hence using 4 stages in your phase
linear filter?
Could you post a brief text summary of your design?
73, Bob ZL2CA
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