Topband: Receivers

[Tom Rauch]

> For minimum phase filters, it is true that a brick
> wall filter inevitably has extremely delay distortion,
> resulting in ringing.  However, for non-minimum phase
> filters, there is no such delay constraint.

Rick and all,

Most amateurs call any form of rise and fall softening "ringing", not just
ringing from phase delay. In order for a filter to be considered "normal
sounding", it has to pass sidebands without significant attenuation out to
perhaps one hundred Hz each side, which would be about 200Hz BW.

Of course filters can get worse than this, but nothing can be better.

I wouldn't want people to think by eliminating phase errors we could tighten
selectivity down to sub-200 Hz ranges without lengthening noise-pulse width
and softening and dragging out the rise and fall times of CW.

As Greg, Bill, and others say too much selectivity is just as bad as not
having any. 250Hz with VERY good filters is about the most I can stand,
unless background noise is just a perfectly smooth hiss (or significantly
weaker than the desired signal).

73 Tom