Bill said:
> Ringing is part of the nature of band pass filtering.
Not entirely so - if the bandpass filtering is Gaussian in transfer function, no
ringing occurs on application of a step function. Generally, Gaussian filters
aren't a lot of use for our 'narrow' point of view (SSB and CW), as they have
insufficient selectivity. It is possible to produce a 'minimum ringing' CW
filter by having a Gaussian 'top' down to about -12dB, and then going into a
Chebycheff shape below that. According to Dave Leeson, W6NL (es W6QHS), a very
badly mismatched CW bandwidth crystal filter can give you a Gaussian or near
Gaussian response, albeit at the penalty of very high (20dB or more) insertion
loss.
Back before W2VJN took over International Radio, I asked them at Dayton about
their CW filters and ringing. I was told that 'Our filters don't ring'. When I
asked if they were Gaussian, he said 'No, but they don't ring'. Hmmmm.......
73
Peter G3RZP
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